Question

The income of a person is Rs. 300000 in the first year and he receives an increase of Rs. 10000 to his income per year for the next 19 years. Find the total amount he received in 20 years.

Answer 1

The income of a person in 1^st year = Rs 300000

The income of a person in 2^nd year = Rs 300000 + 10000

= Rs 310000

The income of a person in 3^rd year = Rs 310000 + 10000

= Rs 320000

and so,on

Therefore, the AP is

300000, 310000, 320000,…

Here a = 300000, d = 310000 – 300000 = 10000

and n = 20

We know that,

⇒ S₂₀ = 10 [600000 + 190000]

⇒ S₂₀ = 10[790000]

⇒ S₂₀ = 7900000

Hence, the total amount he received in 20 years is Rs 7900000.