Question

ramkali saved rs 5 in the first week of a year and then increased her werkly savinhs by rs 1.75 if in the nth week ,her weekly savings become rs 20.75 find n

Answer 1

Ramkali saved in 1st week = 5 ₹

and increase per week = 1.75₹

We absorb here,

5 , 6.75 , 8.5 ,.........20.75 are in AP

where, a = 5 , d = 1.75 and Tn = 20.75

Tn = a + ( n -1)d

20.75 = 5 + (n -1)1.75

15.75 = 1.75(n -1)

9 = n -1

n = 10

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Answer 2

Answer:

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 common difference, d = 1.75

Also given,

an = 20.75

Find, 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, n is 10.