26.
A certain sum of money at compound interest grows up to Rs. 12960 in 2 years and up to Rs. 13176 in 3 years. Find the rate percent per annum.
•  A. 1 1 % 3
•  C. 1 2 % 3
•  B. 2 1 3
• D.
None of these
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Explanation :

 Here, x = 12960, y = 13176, A = 2 and B = 3.

R
 y x
I/B-A - 1    x 100%

 = 13176 - 1 x 100% 12960

 = 216 x 100 % 12960

 = 4 % or 1 1 % 3 3

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27.
On a sum of money, the simple interest for 2 years is Rs. 660, while the compound interest is Rs. 696.30, the rate of interest being the same in both the cases. The rate of interest is:
• A.
10%
• C.
12%
• B.
10.5%
• D.
None of these
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Explanation :

Difference in C.I. and S.I. for 2 years = Rs. (696.30 - 660) = Rs. 36.30.

S.I.  for one year = Rs. 330.

S.I. on Rs. 330 for 1 year = Rs. 36.30.

Rate = 100 x 36.30 % = 11%
330 x 1

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28.
 A tree increases annually by 1 th of its height. By how much will it increase after 2 years, 8
if it stands today 64 cm high?
• A.
72cm
• C.
75cm
• B.
74cm
• D.
81cm
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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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29.
A sum of money amounts to Rs. 10648 in 3 years and Rs. 9680 in 2 years. The rate of interest is
• A.
5%
• C.
15%
• B.
10%
• D.
20%
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Explanation :

Let P be the principal and R% per annum be the rate. Then,

 P 1 + R 3 = 10648 ...(i) 100

 and P 1 + R 2 = 9680 ...(ii) 100

On dividing (i) by (ii), we have

1 + R  = 10648
100 9680

R  = 968 = 1
100 9680 10

R  = 1 x 100 = 10%
10

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30.
Mr. Dua invested money in two schemes A and B offering compound interest @ 8 p.c.p.a. and 9 p.c.p.a. respectively. If the total amount of interest accrued through two schemes together in two years was Rs. 4848.30 and the total amount invested was Rs. 27,000. What was the amount invested in Scheme A?
• A.
Rs. 12,000
• C.
Rs. 15,000
• E.
None of these
• B.
Rs. 13,500
• D.
Cannot be determained
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Explanation :

Let the investment in scheme A be Rs. x

Then, investment in scheme B = Rs. (27000 - x).

x x

 1 + 8 2 - 1 100

+ (27000 - x)
 1 + 9 2 - 1 100
= 4818.30

 x x 104 625

+
 1881(27000 - x) 10000
=
 481830 100

1664x + 1881 (27000 - x) = 48183000

(1881x - 1664x) = (50787000 - 48183000)

217x = 2604000

x = 2604000  = 12000
217

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