Question

Answer the following questions-
1) A sum of money triples itself in 5 years. What is the rate of interest?
2) In how many years, will a sum of money double itself at 16 2/3% p.a. simple interest?

Answer 1

Answer:

1) Assume principal to be 100RS

Amount after 5years = 300RS (since it triples)

Sointrest = 200Rs (principal - amount = interest)

Inorder to become 5times i.e 500RS, interest has to be 400RS on the principal amount which is 100Rs

200RS → 5years -

400RS → ?

= 400*5/200=10years

2) Let the original sum of money be ' x'

after 16 years:

amount = 2 times of original sum

amount = 2 x x = 2x

since, the sum will be doubled in 16 years.

so then, simple interest will be equal to

original sum.

Find the interest:

simple interest = amount - original sum

simple interest = 2x - x = x

Find the rate:

original sum= x=p, time = 16 years

since ,we know thatS.I = (pxrxt) / 100

this implies that,

r=

(S.I x 100) / pxt

r = (x * 100) / x * 16

r = 100/16 = 25 / 4%

r = 6 whole 1/4%

Answer:

required rate of interest = 6 1/4 %