ANSWER KEY
ANSWER KEY
HINTS & SOLUTIONS (YEAR-2011)
HINTS & SOLUTIONS (YEAR-2011)
PART-A (1 Mark)
PART-A (1 Mark)
MATHEMATICS
MATHEMATICS
1. 1. P(x) =P(x) = )) c c a a )( )( b b a a (( )) c c x x )( )( b b x x ((
+ + )) a a b b )( )( c c b b (( )) a a x x )( )( c c x x ((
+ + )) b b c c )( )( a a c c (( )) b b x x )( )( a a x x ((
L Leett ff((xx) ) = = PP((xx) ) – – 11 f(a) = 1 + 0 + 0 – 1 = 0 f(a) = 1 + 0 + 0 – 1 = 0 f(b) = 0 + 1 f(b) = 0 + 1 + 0 + 0 – 1 = 0– 1 = 0 f(c) = 0 + 0 + 1 – 1 = 0 f(c) = 0 + 0 + 1 – 1 = 0f(x) is a polynomial of degree atmost 2, and also attains same value (i.e., 0) for 3 distinct values of x f(x) is a polynomial of degree atmost 2, and also attains same value (i.e., 0) for 3 distinct values of x (i.e. a,b,c).
(i.e. a,b,c).
f(x) is f(x) is an identity with only value equal to zero.an identity with only value equal to zero.
f(x) = 0f(x) = 0
x x
RR
P(x) = 1,P(x) = 1,
x x
RR2.
2. Using cauchy schwartz’s inequalityUsing cauchy schwartz’s inequality (a
(a22 + b + b22) (x) (x22 + y + y22))
(ax + by) (ax + by)22equality holds at equality holds at x x a a = = yybb
ay – bx = 0ay – bx = 0 Aliter : Aliter : a a22 + b + b22==8811 ...((ii)) x x22 + y + y22 = =112211 ...((iiii)) a ax x + + bby y = = 9999 ...((iiiiii)) (a(a22 + b + b22) (x) (x22+ y+ y22) ) = = 881 1 × × 112211 ...((iivv)) [[((ii) ) × × ((iiii))]]
(ax + by)
(ax + by)22 = 99 = 9922 ...((vv)) [[ssqquuaarriinng g ((iiiiii))]]
(iv) – (v) (iv) – (v) Q Quueess.. 11 22 33 44 55 66 77 88 99 1100 1111 1122 1133 1144 1155 1616 1177 1188 1199 2200 Ans. Ans. AA CC AA BB BB DD AA AA AA CC BB CC BB BB CC AA AA CC DD AA Q Quueess.. 2211 2222 2233 2244 2255 2266 2277 2288 2299 3030 3311 3322 3333 3344 3355 3366 3377 3388 3399 4400 Ans. Ans. BB CC CC DD CC BB BB DD AA CC DD CC DD DD AA DD AA AA BB DD Q Quueess.. 4411 4422 4433 4444 4455 4466 4477 4488 4499 5050 5511 5522 5533 5544 5555 5566 5577 5588 5599 6600 Ans. Ans. DD DD BB BB CC BB DD CC BB CC DD AA CC CC AA BB AA BB BB DD Q Quueess.. 6611 6622 6633 6644 6655 6666 6677 6688 6699 7070 7711 7722 7733 7744 7755 7766 7777 7788 7799 8800 Ans. Ans. CC CC BB BB AA BB BB BB CC AA AA CC BB AA AA BB DD CC AA CC
3. 3. Then, Then, aa x x 1 1 x x
and and bb x x 1 1 x x 3 3 2 2
2 2 2 2 a a x x 1 1 x x
x x22 + + 2 2 x x 1 1 +2 = a +2 = a22 ...(i)...(i) 3 3 x x 1 1 x x
= = aa33 x x33 + +
x x 1 1 x x 3 3 x x 1 1 3 3 = a = a 3 3 ...(ii)...(ii)add equation (1) and (2) add equation (1) and (2)
x x 1 1 x x 3 3 2 2 x x 1 1 x x x x 1 1 x x22 33 33 22 = a = a22 + a + a33 b + b +
22
3 3 x x 1 1 x x + 2 + 3a = a + 2 + 3a = a22+ a+ a33 2 2 3 3 x x 1 1 x x
= a= a33 + a + a22 – 3a – b – 2 – 3a – b – 2 4. 4. |a – b| = 2, |b – c| = 3, |c – d| = 4|a – b| = 2, |b – c| = 3, |c – d| = 4 a – b = ± 2 a – b = ± 2 b – c = ± 3 b – c = ± 3 c – d = ± 4 c – d = ± 4possible values of (a – d) are ± 9, ± 5, ± 3 possible values of (a – d) are ± 9, ± 5, ± 3 |a – d| = 9, 5, 3, 1
|a – d| = 9, 5, 3, 1
Sum of all possible values are Sum of all possible values are 1818 5.
5. Given 0 < r < 4Given 0 < r < 4
in all the obtain in all the obtain (Base) (Base)xx = = 5 5 9 9
the option having least base will give the largest x. the option having least base will give the largest x. So, in option B base
So, in option B base
17 17 r r 11 is minimum for 0 < r < 4. is minimum for 0 < r < 4. Aliter : Aliter : (1 + (1 +
xx == 5 5 4 4
x log (1 +x log (1 +
) = log (1.8)) = log (1.8)
For x
For x to be to be maximummaximum log (1 +
log (1 +
) should be minimum) should be minimum
= =
r r oorr 22rr oorr 17 17 r r or or r r 1 1 in 0 < r < 4 in 0 < r < 4 17 17 r r is minimum. is minimum. 6.6. Angle Angle bisector bisector theoremtheorem
6 6 x x = = z z y y x x 66 z z y y 10cm 10cm22
xz = 6yxz = 6y
20 = 6y20 = 6y
y =y = 3 3 10 10 cm cm ALITER : ALITER : LetLet
ACB = ACB =
BC = 6 cosBC = 6 cos
, AB = 6 sin, AB = 6 sin
BD : CD BD : CD = AB : = AB : ACAC = 6 sin = 6 sin
: 6 : 6 = sin = sin
: 1 : 1 BD = BD =
sinsin
sin sin 1 1 cos cos 6 6 ...(i) ...(i) CD =CD = 1166coscossinsin
11
...(ii) ...(ii) BD = CD sin BD = CD sin
Now, area ofNow, area of
ADC = 10 ADC = 10 cmcm222 2 1 1 × 6(CD) sin × 6(CD) sin
= = 1010 CD sin CD sin
= 10/3 cm = 10/3 cm 7. 7.
Slant height = 13Slant height = 13
byby = r = r
2 2
.5 = 13.5 = 13
13 13 10 10
8. 8. x x 12 12 = = 8 8 x x 20 20
xx22 – 20x + 96 = 0 – 20x + 96 = 0 x = 8, 12 x = 8, 12 ALITER : ALITER : B(0,0) B(0,0) C(20,8) C(20,8) E E((xx,,00)) DD((2200,,00)) A(0,12) A(0,12) AC = AC = 202022
4422 == 44 5522
11 == 44 2626
(12(1222 + x + x22) + (8) + (822 + (20 – x) + (20 – x)22) ) = = 202022 + 4 + 422 2x 2x22 – 40x + 400 + (12 – 40x + 400 + (1222 – 20 – 2022) + (8) + (822 – 4 – 422) = 0) = 0 2x 2x22 – 40x + 144 + 12.4 = 0 – 40x + 144 + 12.4 = 0 x x22 – 20x + 72 + 24 = 0 – 20x + 72 + 24 = 0 x x22 – 20x + 96 = 0 – 20x + 96 = 0 x = 12, 8 x = 12, 8 9. 9. AP = 2 sin AP = 2 sin 60° =60° = 33
d =d = 22
33 10. 10. 51251233 – (253 – (25333 + 259 + 25933)) = 512 = 51233 – [(512) (253 – [(512) (25322+ 259+ 25922 – 253.259)] – 253.259)] = 512 (512 = 512 (51222 – ((512) – ((512)22 – 3(253)(259)) – 3(253)(259)) = 512 (3.253 – 259) = 512 (3.253 – 259) = 2 = 299. 3. 253 . 7.37. 3. 253 . 7.37 = 2 = 299. 3. (11) . (23). 7.37. 3. (11) . (23). 7.37So, number of distinct prime divisors are 6. So, number of distinct prime divisors are 6. 1
11.1. TTop layer has (13 × op layer has (13 × 13) balls13) balls
Simillary one layer below top layer will have (14 × 14) balls and we have 18 lesens to t
Simillary one layer below top layer will have (14 × 14) balls and we have 18 lesens to t otal number of ballotal number of ball N = (13) N = (13)22 + (14) + (14)22 + ...+ (30) + ...+ (30)22 N = N = 6 6 61 61 31 31 30 30
– – 6 6 25 25 13 13 12 12
N = 8805 N = 880512.
12. Let distance is 6dLet distance is 6d M Muudd :: TTaarr :: SSttrreeaamm D Diissttaannccee dd :: 33dd :: 22dd S Sppeeeedd 33VV :: 55VV :: 44VV time time V V 3 3 d d :: V V 5 5 d d 3 3 :: V V 4 4 d d 2 2
1100 :: 1188 :: 1155 ((NNootte e : : oorrddeer r iis s cchhaannggeed d iin n qquueessttiioonnss)) 13.13. 3 step3 step
14.
14. The clock well show 1 in an hour for 19 timThe clock well show 1 in an hour for 19 tim e for 11 hours it will show the incorrect time for (19 × 11) time.e for 11 hours it will show the incorrect time for (19 × 11) time. The last 12
The last 12thth hour will always show the incorrect time so total incorrect tim hour will always show the incorrect time so total incorrect tim ee
(19 × 11 + 60) min = 269 min (19 × 11 + 60) min = 269 min
there are 24 hours in a day to = 269 × 2 = 538 min there are 24 hours in a day to = 269 × 2 = 538 min 538 min = 538 min = 30 30 269 269 = = 9 h9 houoursrs
the fraction day when the clock shows correct tim the fraction day when the clock shows correct tim e is =e is =
24 24 9 9 1 1
= = 8 8 5 5 8 8 3 3 1 1
15. 15. RiRighght t WrronW ong g UnUnaatttetempmptetedd 1 155 1155 00 14 14 44 13 13 88 1 122 1122 1 111 1166 1 100 2200 6 cases only 6 cases only
PHYSICS
PHYSICS
16.
16. By mechanical energy conservationBy mechanical energy conservation KE KEii + + UUii = = KEKEf f + + UUf f O + U O + Uii = 0 + U = 0 + Uf f U Uii = U = Uf f h hii = h = hf f
So D will lie on line AB So D will lie on line AB 17.
17. Since toy is not accelerating so net external forSince toy is not accelerating so net external for ce on toy is zero. So (A)ce on toy is zero. So (A)
18. 18. |S |S11| + |S| + |S22| = H| = H 2 2 gt gt 2 2 1 1 + ut – + ut – gtgt22 2 2 1 1 = H = H u ut t = = H H .. ...((II)) H = H = g g 2 2 u u22 ....(II) ....(II) t = t = 22uugg S S22 = ut – = ut – gtgt22 2 2 1 1 = = 3388uugg g g 4 4 u u g g 2 2 1 1 g g 2 2 u u 4 4 2 2 2 2 2 2 = = HH 4 4 3 3 19. 19.
By concept of centre of mass By concept of centre of mass 36x = 9(20–x) 36x = 9(20–x) 36x = 180 – 9x 36x = 180 – 9x 45x = 180 45x = 180 x = 4m x = 4m 20.
20. All three wi All three will be ll be in thermal equilibrium in thermal equilibrium with air with air of room. so of room. so temperature of the temperature of the three will three will be samebe same 21.
21. Pressure of gas is same Pressure of gas is same everywhere in the vessel.everywhere in the vessel. 22.
22. TTo travel from P to Q in minimum o travel from P to Q in minimum time, she should travel on path PCQ.time, she should travel on path PCQ. 23. 23. i = 45°i = 45°
C C C = 45° for minimum C = 45° for minimum
sin 45 = 1 sin 45 = 1
== 22 = 1.42 = 1.4224. 24.
In this case only half part of lens
In this case only half part of lens is used to form is used to form the image so intensity will reducethe image so intensity will reduce
25. 25. R =R = A A R = R = A A R = R = V V 2 2
R = R = V V )) 2 2 (( 22
= 4R = 4R 26. 26. EE11 = Electric field due to +Q = Electric field due to +Q E
E22 = Electric field due to –2Q = Electric field due to –2Q There resultant is 0 at this point There resultant is 0 at this point
27. 27.
= = 100100 750 750 tt // mgh mgh = = 100100 750 750 60 60 6 6 10 10 300 300 = = 100100 750 750 300 300 = = 40%40% 28. 28.29. 29. pbpb3143148282
2e 2e –1 –1 + + 44 2 2 He He + + XX8282210210So 82 proton and 128 Neutron So 82 proton and 128 Neutron 30. 30. PV = NKTPV = NKT 10 1055 × 100 = N × 1.38 × 10 × 100 = N × 1.38 × 10 –23 –23 × 273 × 273 N N
3 3 × × 10102727CHEMISTRY
CHEMISTRY
31.31. Since pressures of the gases are same Since pressures of the gases are same in both the containers. So, the final pressure will not changein both the containers. So, the final pressure will not change 32.
32. Reativity towards Friedel-Crafts alkylation is prReativity towards Friedel-Crafts alkylation is pr oportional to electron density in the benzene ring.oportional to electron density in the benzene ring.
33. 33. n = 2n = 2 l = 0, 1 l = 0, 1 m m = 0, = 0,
1 1 1 1 0 0 34.34. Average Average Kinetic Kinetic Energy Energy depends depends only only on teon temperaturemperature (KE)
(KE)avgavg = = 2 2 kT kT 3 3 per molecule per molecule 35.
35. Ideal gasIdeal gas
H = 0H = 0
S > S > 00 (randomness increases) (randomness increases) 36. 36. (NH(NH44))22 Cr Cr 22OO77
Cr Cr 22OO33 + N + N22 + + 4H4H22OO 37.37. Acc Accordording ing to to the the gragraph ph solusolu bilibility ty 40° 40° is is apprappr ox. ox. 200 200 g g per per 100 100 mlml. . For For 50 50 ml, ml, amoamount unt is is 100 100 gg approx.
approx.
38.
38. Aldehyde, ketones Aldehyde, ketones with acetywith acetyl group CHl group CH33 – – – show – show Iodoform test.Iodoform test.
39. 39. 16 16 1 1 2 2 1 1 n
n
n, number of half-lives = n, number of half-lives = 4 = 2 hrs. hal4 = 2 hrs. half-life = 30 min.f-life = 30 min.40.
40. ZnSZnS
ZnSOZnSO44 during roasting, sulphide ore is during roasting, sulphide ore is converted into sulphate.converted into sulphate.41. 41. 42. 42. ClCl22 + 2KBr + 2KBr → → 2KCl + Br 2KCl + Br 2 2 reddish brown reddish brown
43.
43. (i) and (iv) are hetro aromatic (i) and (iv) are hetro aromatic and the resonance form of azulene (iii) is aromand the resonance form of azulene (iii) is arom atic.atic.
(ii) Is nonaromatic. (ii) Is nonaromatic.
44.
44. Simple nomenclature of alkane.Simple nomenclature of alkane. 45.
45. The major product formed in the reaction :The major product formed in the reaction :
Product is : Product is : ((AA))ii ((BB)) iiii ((CC))iiiiii ((DD))iivv S Sooll. . ((CC))
The given reaction is S
The given reaction is SNN2 which occurs at sp2 which occurs at sp33 carbon with good leaving group. carbon with good leaving group.
PART-II (2 Marks)
PART-II (2 Marks)
MATHEMATICS
MATHEMATICS
61. 61. f(x) = axf(x) = ax22 + + bbx x + + cc,, ff((11) ) = = 00 g giivveenn,, f(f(11) ) = = 00 a + b + c = 0 a + b + c = 0 a anndd 440 0 < < ff((66) ) < < 5500 40 < 36a + 6b + c < 50 40 < 36a + 6b + c < 50 40 < 35a + 5b < 50 40 < 35a + 5b < 50 8 < 7a + b < 10 8 < 7a + b < 10 7 7a a + + b b = = iinntteeggeer r = = 99 ...((11)) a anndd 660 0 < < ff((77) ) < < 7700 60 < 49a + 7b + c < 70 60 < 49a + 7b + c < 70 60 < 48a + 6b < 70 60 < 48a + 6b < 70 10 < 8a + b < 11.6 10 < 8a + b < 11.6 8 8a a + + b b = = 1111 ...((22)) solving equation (1) and (2)solving equation (1) and (2) a = 2, b = –5, so c = 3 a = 2, b = –5, so c = 3 f(x) = 2x
62.
62. We can write the expression asWe can write the expression as
2011 2011 2 2 r r 22 2 2 1 1 r r 1 1 r r = =
1 1 r r 1 1 r r 2 2 1 1 = =
11
r r
1111
r r 1
111
Putting r = 2, 3, ..., 2011 Putting r = 2, 3, ..., 2011 = 2010 + 1 + = 2010 + 1 + 2011 2011 1 1 2012 2012 1 1 2 2 1 1
= 2011 + = 2011 + 2211
2011201111
2012201211
this lies between (2011, 2011 this lies between (2011, 2011
2 2 1 1 )) 63.
63. Let initially 2 bases have radii 5 & Let initially 2 bases have radii 5 & r. and finally bases have radii (1.21 × 5) & r. and finally bases have radii (1.21 × 5) & r.r.
Ratios of volumes =Ratios of volumes = 11..2121 V V V V 1 1 2 2
V V22 = = 3 3 h h
((6.05) ((6.05)22 + 6.05 r + r + 6.05 r + r 22)) V V11 = = 3 3 h h
(5 (522 + 5r + r + 5r + r 22)) 21 21 .. 1 1 V V V V 1 1 2 2
11..2121 r r r r 5 5 5 5 r r r r 05 05 .. 6 6 )) 05 05 .. 6 6 (( 2 2 2 2 2 2 2 2
36. 36.6026025 + 65 + 6.0.055 r +r + r r 22 = 30.25 + 6.05r + 1.21 r = 30.25 + 6.05r + 1.21 r 22 .21r .21r 22 = 6.3525 = 6.3525 r r 22== 21 21 .. 3525 3525 .. 6 6 r = r = 2 2 11 11 cm. = 55 mm cm. = 55 mm 64.64. Let speed of B = V km/hr.Let speed of B = V km/hr. Let speed of A = 3V km/hr. Let speed of A = 3V km/hr. Given 4r = 2 × 60 km/hr
Given 4r = 2 × 60 km/hr
V = 30 km/hr V = 30 km/hrDistance covered by then after 10 min. = 2 × 10 = 20 k Distance covered by then after 10 min. = 2 × 10 = 20 k mm So, remaining distance = (30 – 20) km = 10 km.
So, remaining distance = (30 – 20) km = 10 km. Time table b
Time table by B to coy B to cover 10 kmver 10 km == 30 30 10 10 = 20 min = 20 min 65. 65. A A BB CC 1 10 0 hhrr 220 0 hhrr 330 0 hhr r Exactly one pair of taps is open during
Exactly one pair of taps is open during each hour and every pair of taps is each hour and every pair of taps is open at least for open at least for one hour.one hour. So
20 20 1 1 10 10 1 1 + +
202011
303011
+ +
303011
101011
= = 60 60 22 22 FirstFirst then then second second then then Third Third thenthen
In three hours the tank will be f In three hours the tank will be f illedilled
th th 60 60 22 22
part partNow, for minimum tim
Now, for minimum tim e, the rest tank me, the rest tank m ust be filled with A and B taps.ust be filled with A and B taps.
60 60 9 9 20 20 1 1 10 10 1 1So, the rest So, the rest
th th 60 60 38 38
Part of tank will take 5 hour more Part of tank will take 5 hour more So, the tank will be filled in 8
So, the tank will be filled in 8thth hour. hour.
PHYSICS
PHYSICS
66. 66. kx kx11 + +
11vg vg ==
vgvg v = v = ggkxkx gg 1 1 1 1 kx kx22 + +
22vg vg ==
vgvg v = v = ggkxkx gg 2 2 2 2 g g )) (( kx kx g g )) (( kx kx 2 2 2 2 1 1 1 1
xx11 – –
xx11 = =
xx22 – –
xx22
xx11 – x – x22) =) =
xx11 – –
xx22
= = 2 2 1 1 2 2 1 1 1 1 2 2 x x x x x x x x 67. 67. 22f f 22ii 8 8 4 4 mv mv 2 2 1 1 mv mv 2 2 1 1 dx dx .. F F
2 2 1 1 × 3 × 8 – × 3 × 8 – 2 2 1 1 × 1.5 × 4 = × 1.5 × 4 = 2 2 1 1 × 0.5 (v × 0.5 (vf f 22 – 3.16) – 3.16)22 24 – 6 = 0.5 (v 24 – 6 = 0.5 (vf f 22 – 3.16 – 3.1622))68. 68. v vii = = vvf f 2 2 5 5 ×1 × V + ×1 × V + 2 2 5 5 × 0.5 × 4v = × 0.5 × 4v = 2 2 5 5 P 5V P 5V 3V = 5PV 3V = 5PV P = P = 5 5 3 3 = 0.6 = 0.6 69. 69. sin(90 –
sin(90 –
) =) =
sinr sinr cos cos
= = 4 4 x x h h 2 2 // x x 3 3 4 4 2 2 2 2 cos cos
== 4 4 1 1 x x h h 1 1 3 3 2 2 2 2 2 2 == 16 16 4 4 16 16 49 49 1 1 3 3 2 2 = = 53 53 4 4 3 3 2 2 = = 53 53 3 3 8 8 70. 70. P Pii = i = i22RR P = P = 16 16 100 100 1 1 4 4 10 10 22
P Pf f = i = i22RR 100 100 100 100 10 10
22
CHEMISTRY
CHEMISTRY
71.
71. 100 mL 0.1 M CH100 mL 0.1 M CH33COOH 50 mL 0.4 M COOH 50 mL 0.4 M CHCH33COONaCOONa
ChCh COOHCOOH
COO COO CH CH 3 3 3 3 = 1 = 1 pH = pKa + log 1 pH = pKa + log 1 = pKa = 4.76 = pKa = 4.76 72.72. 9-structural isomers are possible.9-structural isomers are possible. CH CH33CHCH22CC
CCHH,, CCHH33 –C –C
C–CHC–CH33 CH CH22=CH–CH=CH=CH–CH=CH22,, CHCH22=C=CH–CH=C=CH–CH33 73. 73. 74.74. CoCo+3+3 : 3d: 3d664545°° ststrorong ng fifieleld ld ligiganand (d (NHNH 3 3)) Ni Ni+2+2 : 3d: 3d8845° 45° SFL SFL (NH(NH 3 3)) Cr Cr +3+3 : 3d: 3d3345° 45° WFL (HWFL (H 2 2O)O) Fe Fe+2+2 : 3d: 3d66 45 45° ° WFL (HWFL (H 2 2O)O) Co
Co+3+3 will bwill be diamagnetic e diamagnetic (i)(i)
75.
75. ReReacactition on ququototririenent t Q Q ==
]] [[ ]] H H [[ ]] H H [[ 2 2 2 2 2 2
= = 2 2 .. 0 0 1 1 .. 0 0 )) 4 4 .. 0 0 (( 22
= 8= 8 Q < Q < KKreaction proceeds in the forward direction. reaction proceeds in the forward direction.