A sum was lent at 20% p.a compound interest, the interest being compounded annually. Rs. 1200 was paid back after 1 year. after another year rs. 1440 was repaid to clear the loan. find the sum lent? 

1200/1.2 + 1440/1.2*1.2 = 2000rs.

consider 2nd year. he has paid 1440 and clear the debt.

so the let amount remaining after 1st year (giving 1200) be 'P'

p(1+(20/100))^1=1440

p=1200

so the total amount after 1st year =1200+1200=2400

p(1+(20/100))^1=2400

p=2000