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Ramkali saved Rs 5 in the first week of a year and then increased her weekly saving by Rs 1.75. If in the *n*^{th}week, her week, her weekly savings become Rs 20.75, find *n.*

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#### Solution

Given that,

a = 5

d = 1.75

a_{n} = 20.75

n = ?

a_{n} = a + (n − 1) d

20.75 = 5 + (n - 1) × 1.75

15.75 = (n - 1) × 1.75

`(n - 1) = 15.75/1.75 = 1575/175`

`= 63/7 = 9`

n - 1 = 9

n = 10

Hence, n is 10.

Concept: nth Term of an AP

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