Question

A certain sum amounts to rs. 7000 in 2 years and to rs. 8000 in 3 years. find the sum.

Answer 1

"Interest for 1 year is the same whether it's simple interest or the compound interest.

Now interest of third year = 8000 - 7000 = 1000; means principal for this interest is 7000 if comound interest is taken

If 7000 is the principal interest = 1000

if 100 is the principal interest =(1000/7000) * 100 = 100 %

When a thing increases for two successive times the overall increase on initial amount = a + b + (a * b)/100

Therefore overall interest for two years = 100 + 100 + [(100)*(100)]/100 = 300 %

Therefore amount after 2 years = 100 + 300 = 400

If 400 is the amount principal =100

if 7000 is the amount principal =(900/100)*7000 =63000

So sum = 63000;

"