Question

The time by which a sum of money is 8 times of itself it is doubles itself in 15
(a) 42 years
(b) 43 years
(c) 45 years
(a) 46 years
What is the rate of simple interest if a sum of money amounts to Rs. 2,784 in 4 years and Rs. 2,688 in 3 years
(a) 1% p.a.
(d) 8% p.a.
(b) 4% p.a.
(c) 5% p.a.
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Answer 1

Answer:

1.45 years

A sum of money doubles itself at a compound interest in 15 years . In how may years it will become 8 times ?? If the sum doubles (x2) in 15 years, then it to become 2*2*2 = 8 times as large it should double three times, so three 15 years time period are needed, which is 3*15 = 45 years.

2.4%

Amount in 3 years = Rs. 2688

Amount in 4 years = Rs. 2784

Thus, interest per year = 2784 - 2688 = Rs. 96

Principal amount = 2688 - (3 x 96) = Rs. 2400

Interest percentage = 96 / 2400 = 4%

Answer 2

Answer:

the time by which a sum of money is 8 times of it self is doubles itself in 15?

A=p(1+r/100)^15

2p=p(1+r/100)^15

2=(1+r/100)^15

m is time

p(1+r/100)^m=8p

(1+r/100)^m=8

(1+r/100)^m=2^3

1+r/100)^m=1+r/100)^15^3

m=45