Question

₹ 800 per month is deposited in an R.D. account for one and half years. If the depositor gets ₹ 2,280 as interest at the time of maturity, the rate of interest is ______.

विकल्प

• 20%

• 15%

• 10%

• 12%

Answer 1

₹ 800 per month is deposited in an R.D. account for one and half years. If the depositor gets ₹ 2,280 as interest at the time of maturity, the rate of interest is 20%.

Explanation:

P = ₹ 800,

n = `1 1/2` years

= `(3/2 xx 12)` months 

= 18 months

And I = ₹ 2280

We know that

`I = P xx (n(n + 1))/(2 xx 12) xx R/100`

`\implies 2280 = 800 xx (18 xx 19)/(2 xx 12) xx R/100`

`\implies` R = `2280 xx (2 xx 12)/(18 xx 19) xx 100/800`

`\implies` R = 20