Question

A person borrowed Rs.500 @ 3% per annum S.I. and Rs.600 @ 4.5% per annum on the agreement that the whole sum will be returned only when the total interest becomes Rs.126. The number of years, after which the borrowed sum is to be returned, is:

Answer 1

Interest=PRT/100, I(1) =500*3/100*1 =15 I(2)=600*4.5/100*1 =27,since we are looking for T=time I(r)= 15 per annum I(2)=27 per annum (I(1) +I(2))=15+27=42 in 2 annums, if 2 annums=42,then how many annums for 126(total interest),assume time =a,then,if 2y=42,a=126,cross multiple=42a=2(126),a=252/42=6,then if T[1]+T[2]=6,then 2T=6,T=3 T=3