What equal instalment of annual payment (in ₹) will discharge a debt that is due as ₹624 at the end of 5 years at 2% per annum simple interest?

Let the annual installment be ₹x.
The total debt is to be discharged in 5 years.

The first installment paid at the end of year 1 will earn interest for (5−1)=4 years.
The second installment paid at the end of year 2 will earn interest for (5−2)=3 years.
The third installment paid at the end of year 3 will earn interest for (5−3)=2 years.
The fourth installment paid at the end of year 4 will earn interest for (5−4)=1 year.
The fifth installment paid at the end of year 5 will earn no interest.

The sum of all these amounts equals the total due debt of ₹624:

(x+
100
x×2×4
​
)+(x+
100
x×2×3
​
)+(x+
100
x×2×2
​
)+(x+
100
x×2×1
​
)+x=624
5x+
100
2x
​
(4+3+2+1)=624
5x+
100
2x×10
​
=624
5x+
100
20x
​
=624
5x+0.2x=624
5.2x=624
x=
5.2
624
​
=
52
6240
​
=120
The equal annual installment is ₹120.