Question

a sum of money become 8/5 of itself in 5 years at a certain rate of simple interest .find the rate of interest

Answer 1

If P= 1
I = 3/5(8/5-1=3/5)
3/5= 1×5×R/100
3/5 × 20= 12%
Checking
If P = 100,
then,
3/5= 100×5×12/100
3/5=60
A=160
160/100=8/5

Answer 2

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Refer to the attachment!