Ramkali saved Rs. 5 in the first week of a year and then increased her weekly saving by Rs. 1.75. If in the nth week, her weekly saving become Rs. 20.75, find $n$.

Given:

Ramkali saved Rs. 5 in the first week of a year and then increased her weekly saving by Rs. 1.75.

In the nth week, her weekly saving becomes Rs. 20.75.

To do: 

We have to find $n$.

Solution:

Her weekly saving will be an A.P

Let

$a = 5, d = 1.75 , a_n= 20.75$

$a_n = a+(n-1)d$

$5+(n-1)1.75 = 20.75$

$5+1.75n -1.75 = 20.75$

$1.75n= 20.75+1.75-5$

$1.75n= 22.50-5$

$1.75n = 17.50$

$n = \frac{17.50}{1.75}$

$n = 10$

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Updated on: 10-Oct-2022

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