Question

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.

Answer 1

Answer:

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

Step-by-step explanation:

Answer 2

$\huge \sf \red{Solution.}$

Here,

a = ₹ 5

d = ₹ 1.75

aₙ = ₹ 20.75

We know that

aₙ = a + ( n – 1 ) d

$20.75 = 5 + (n - 1)(1.75)$

$(n - 1)(1.75) = 20.75 - 5$

$(n - 1)(1.75) = 15.75$

$n - 1 = \frac{15.75}{1.75}$

$= \frac{1575}{175} = \frac{315}{35}$

$n - 1 = \frac{63}{7}$

$n - 1 = 9$

$n = 10$

Hence, the required value of n is 10.