A man saved Rs 66000 in 20 years.

Question:

A man saved Rs 66000 in 20 years. In each succeeding year after the first year he saved Rs 200 more than what he saved in the previous year. How much did he save in the first year?

Solution:

Given the total amount saved in 20 years is 66000 hence S20 = 66000

Let the amount saved in first year be ‘a’

Then as he increases 200 Rs every year then the amount in second year will be ‘a + 200’ then in third year ‘a + 400’ and so on

The sequence will be a, a + 200, a + 400…

The sequence is AP and the common difference is d = 200

There are 20 terms in the sequence as he saved money for 20 years

Using the sum formula for AP S= n/2 (2a + (n – 1) d) we get

Where n is number of terms a is the first term and d is the common difference

Given that S20 = 66000

S20 = (20/2) (2a + (20 – 1) 200)

⇒ 66000 = 10(2a + 19 × 200)

⇒ 6600 = 2a + 3800

⇒ 6600 – 3800 = 2a

⇒ 2a = 2800

⇒ a = 1400

Hence amount saved in first year is 1400 Rs.

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