Question

₹ 2000 is invested at 10 p.c.p.a. simple interest. Check at the end of the every year whether the interest amount is in A.P. or not. If this is an A.P., then find interest amount after 10 years.

Answer 1

`"SI" = ("P" xx "N" xx "R")/100`

Here, P = ₹ 2000, R = 10 p.c.p.a

Interest at the end of 1^st year

= `(2000 xx 1 xx 10)/100`

= ₹ 200

Interest at the end of 2^nd year

= `(2000 xx 2 xx 10)/100`

= ₹ 400

Interest at the end of 3^rd year

= `(2000 xx 3 xx 10)/100`

= ₹ 600

₹ 200, ₹ 400, ₹ 600, ....forms an A.P.

Here,

a = t₁ = 200,

d = 400 − 200

= 200,

t₁₀ = ?

t_n = a + (n − 1) d    ....(Formula)

By substituting the given values we get,

∴ t₁₀ = 200 + (10 − 1) × 200    ....(Substituting the value)

= 200 + 9 × 200

= 200 + 1800

= 2000

∴ The interest after 10 years is ₹ 2000.