Question

A certain sum of money at certain rate of interest becomes rs 3420 after 2 years and at same rate after two and a half years becomes rs 3525. Find the rate percent per annum.

Answer 1

Answer:

r = 70%

Step-by-step explanation:

P becomes 3,420 at 2 years and after 2.5 years it becomes 3,525

In simple interest,

An= P(1+nr/100)

Given, (i) An = 3,420 , n = 2

3,420 = P(1+2r/100)

3,420×100 = P(100+2r)

3,42,000 = P(100+2r)-----(1)

(ii) An = 3,525 ,n = 2.5

3,525 = P(1+2.5r/100)

3,525×100 = P(100+2.5r)

3,52,500 = P(100+2.5r)----(2)

(2)-(1) =>> 10,500 = 2.5pr-2pr

=>> 10,500 = 0.5pr

pr =21,000

Substitute p = 21,000/r in equation (1)

3,42,000 = 21,000/r(100+2r)

3,42,000r = 21,000(100+2r)

342r = 21(100+2r)

342r = 2,100+42r

342r-42r = 2,100

300r = 2,100

r = 70%