Question

suppose you have 12000 rupees to invest you have to invest sunand at 10% and the rest at 15% how much should be invested at each rate to yield 12% on total amount

Answer 1

Let x be the amount should be invested @10
So 12000-x @ 15%
Interest earned in 10%=x/10
Interest earned in 15%=(12000-x)15/100
=(36000-3x)/20
Interest on 12000@12%=1440
Total interst earned=12% of 12000
x/10+1800-3x/20=1440
-x/20=-360
x=7200 @10%
And 4800@15%