The annual instalment (in ₹) to discharge a debt of ₹8,432 due in 4 years at 16% simple interest per annum is:

Let the annual installment be ₹x.
The debt is due in 4 years at 16% Simple Interest.

The total amount cleared at the end of 4 years by individual installments is:

1st installment clears: x+
100
x×16×3
​
=x+0.48x=1.48x

2nd installment clears: x+
100
x×16×2
​
=x+0.32x=1.32x

3rd installment clears: x+
100
x×16×1
​
=x+0.16x=1.16x

4th installment clears: x

Summing these up to find total debt discharged:

1.48x+1.32x+1.16x+x=8432
4.96x=8432
x=
4.96
8432
​
=
496
843200
​
=1700
Thus, the annual installment is ₹1,700.