# Find the rate of interest compounded annually if an annuity immediate at ₹20,000 per year amounts to ₹2,60,000 in 3 years. - Mathematics and Statistics

Sum

Find the rate of interest compounded annually if an annuity immediate at ₹20,000 per year amounts to ₹2,60,000 in 3 years.

#### Solution

Given, C = ₹20,000, A = ₹2,60,000, n = 3 years.

Now, A = "C"/"i"[(1 + "I")^"n" - 1]

∴ 2,60,000 = (20,000)/"i"[(1 + "i")^3 - 1]

∴ (2,60,000)/(20,000) = (1)/"i" [1 + 3"i" + 3"i"^2 + "i"^3 - 1]

∴ 13 = (3"i" + 3"i"^2 + "i"^3)/"i"

∴ 13 = 3 +  3i + i2
∴ i2 + 3i – 10 = 0
∴ i2 + 5i – 2i – 10 = 0
∴ i(i + 5) – 2(i + 5) = 0
∴ (i + 5)(i – 2) = 0
∴ i = – 5 or i = 2
But, i cannot be negative.
∴ i = 2
∴ "r"/(100) = 2
∴ r = 200% p.a.
∴ The rate of interest is 200% p.a.

Concept: Annuity
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#### APPEARS IN

Balbharati Mathematics and Statistics 2 (Commerce) 12th Standard HSC Maharashtra State Board
Chapter 2 Insurance and Annuity
Exercise 2.2 | Q 1.09 | Page 28