Mathematics
Ramkali saved ₹5 in the first week of a year and then increased her weekly savings by ₹1.75. If in the nth week, her weekly savings become ₹20.75, find n.
AP
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Answer
Weekly savings :
5, 6.75, 8.5, ……….., 20.75
The above list is an A.P. with first term (a) = 5 and common difference (d) = 6.75 - 5 = 1.75
Given,
In nth week, weekly savings become ₹20.75
∴ an = 20.75
⇒ a + (n - 1)d = 20.75
⇒ 5 + (n - 1) × 1.75 = 20.75
⇒ 5 + 1.75n - 1.75 = 20.75
⇒ 1.75n + 3.25 = 20.75
⇒ 1.75n = 20.75 - 3.25
⇒ 1.75n = 17.5
⇒ n =
Hence, n = 10.
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