21.
The difference between compound interest and simple interest on an amount of Rs. 15,000 for 2 years is Rs. 96. What is the rate of interest per annum ?
• A.
8
• C.
12
• E.
None of these
• B.
10
• D.
Cannot be determined
• Report
Explanation :

15000 x
 1 + R 2 100
- 15000   -
 15000 x R x 2 100
= 96

15000
 1 + R 2 100
- 1 -
 2R 100
= 96

15000
 (100 + R)2-10000-200R 10000
= 96

R2 = 96 x 2  = 64
3

R = 8.

 Rate = 8%.

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22.
 A tree increases annually by 1 th of its height. By how much will it increase after 2 years, if 8
it stands today 64 cm high?
• A.
72 cm
• C.
75 cm
• B.
74 cm
• D.
81 cm
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Explanation :

 Increase% = 1 x 100 % = 12.5% 8

 Height after 2 years = 64 x 1 + 25 2 2 x 100

 = 64 x 9 x 9 8 8

 = 81 cm

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23.
The difference between the compound interest and the simple interest on Rs. 8000 for 3 years at 5% per annum is
• A.
Rs. 61
• C.
Rs. 65
• B.
Rs. 63
• D.
None of these
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Explanation :

 We have,

C.I. - S.I. = P
 R 100
3 + 3
 R 100
2

= 8000
 5 100
3 + 3
 5 100
2

 [Here, P = 8000 and R = 5]

= 8000
 125 + 7500 100 x 100 x 100

 = Rs. 61

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24.
The difference between the simple interest on a certain sum at the rate off 10% per annum for 2 years and compound interest which is compounded every 6 months is Rs. 124.05. What is the principal sum?
• A.
Rs. 6000
• C.
Rs. 10,000
• E.
None of these
• B.
Rs. 8000
• D.
Rs. 12,000
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Explanation :

Let the sum be Rs. P. Then

P
 1 + 5 4 100
- 1   =
 P x 10 x 2 100
= 124.05

P
 21 4 20
- 1 -
 1 5
= 124.05

P
 194481 - 6 160000 5
=
 12405 100

P
 194481 - 192000 160000
=
 12405 100

P =
 12405 x 160000 100 2481
= 8000

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25.
A sum of Rs. 550 was taken as a loan. This is to be repaid in two equal annual instalments. If the rate of interest be 20% compounded annually then the value of each instalment is
• A.
Rs. 421
• C.
Rs. 360
• B.
Rs. 396
• D.
Rs. 350
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Explanation :

Let the value of each instalment be Rs. x

Then,
x
 +
x
 1 + 20 100
 1 + 20 2 100
= 550

5x + 25x  = 550
6 36

55x  = 550
36

 x = 360

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