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

Explanation

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



`a_n = a + (n - 1)d` is the nth term of AP.


Here, a is the first term, d is a common difference and n is the number of terms.


From the given data, Ramkali’s savings in the consecutive weeks are `₹ 5, ₹ (5 + 1.75), ₹ (5 + 2 × 1.75), ₹ (5 + 3 × 1.75) ...` and so on
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