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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 nthweek, her week, her weekly savings become Rs 20.75, find n. - Mathematics

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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 nthweek, her week, her weekly savings become Rs 20.75, find n.

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Solution

Given that,

a = 5

d = 1.75

an = 20.75

n = ?

an = 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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APPEARS IN

NCERT Class 10 Maths
Chapter 5 Arithmetic Progressions
Exercise 5.2 | Q 20 | Page 107
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