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, fher weekly savings become Rs 20.75, find n.
Mathematics
Class 10
2596
Alexandria
Solution:
Given that, Ramkali saved Rs.5 in the first week and then started increasing her savings each week by Rs.1.75.
Hence, First term, a = 5 and the common difference is d = 1.75
Also given, an = 20.75 then Find the value of n, i.e. n = ?
As we know, by the nth term formula, an = a + (n − 1) d, therefore,
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, the value if n is 10.