Deepak lent Rs. 8800 to Jaichand for 13 years and Rs. 5500 to Kapil for 12 years on simple interest at the same rate of interest and received Rs. 14432 in all from both of them as interest. The rate of interest per annum is:

Let the common rate of interest per annum be R%.
The formula for Simple Interest is:

SI=
100
P×R×T
​

Interest from Jaichand:

SI
1
​
=
100
8800×R×13
​
=88×13×R=1144R
Interest from Kapil:

SI
2
​
=
100
5500×R×12
​
=55×12×R=660R
Total interest received is Rs. 14432:

SI
1
​
+SI
2
​
=14432
1144R+660R=14432
1804R=14432
R=
1804
14432
​
=8%
Thus, the rate of interest per annum is 8%.