Question

certain rate of simple interest a sum of 6400 rupees becomes 8000rupees in 2 years what sum of money will becomes 15510 in 3 years at the same rate of interest?

Answer 1

Rate of interest is unknown.  Let us assume it as r.

Amount invested P = 6400

Amount received with interest = 8000

Tensure = 2 years

Interest for 2 years for 6400 = 8000-6400 = 1600

Simple interest = PNR/100 = 6400(2)r/100 = 1600

Simplify to get r = 12.5%

---------------------------

II Part:

Now rate of interest is known = 12.5%

P is not known.

Final amount 15510/-

Tenure = 3 years

Final amount = P+PNR/100 = 15510

i.e. P(1+3*12.5/100) 15510

Simplify to get

P (1.375) = 15510

P = 15510/1.375 = 11280/-.