Question

Rohit and Vinay both opened a recurring deposit account in a bank for 2 years at 8% simple interest. Vinay deposited ₹ 300 per month. On maturity, Rohit’s interest was ₹ 800 more than Vinay’s interest. Find:

1. interest earned by Vinay.
2. sum deposited by Rohit every month.

Answer 1

Given: Time = 2 years = 24 months

r = 8%

Formula: I = `(P xx n(n + 1))/2 xx r/(12 xx 100)`

(a) P = ₹ 300 for Vinay

⇒ I = `(300 xx 24(24 + 1))/2 xx 8/1200`

⇒ I = `(300 xx 24(25))/2 xx 8/1200`

⇒ I = `300 xx 600/2 xx 8/1200`

⇒ I = `300 xx 300 xx 8/1200`

⇒ I = 300 × 2

⇒ I = 600

Hence, interest earned by Vinay = ₹ 600.

(b) Rohit’s interest is ₹ 800 more than Vinay’s.

Interest earned by Rohit = ₹ 600 + ₹ 800 

= ₹ 1400

Let Rohit deposit ₹ P per month.

⇒ I = `(P xx 24(24 + 1))/2 xx r/(12 xx 100)`

⇒ 1400 = `(P xx 24(25))/2 xx 8/1200`

⇒ 1400 = `(P xx 600)/2 xx 8/1200`

⇒ 1400 = `P xx 300 xx 8/1200`

⇒ 1400 = 2P 

⇒ P = `1400/2`

⇒ P = 700 

Hence, Rohit deposits ₹ 700 per month.