Question

In a tour, I spent every day as many ten-rupee notes as the number of days I had been away from the home. My total expenditure was 18,300. How long did I stay away from home?

पर्याय

• 1 month

• 2 months

• 3 months

• 4 months

Answer 1

2 months

Explanation:

Let man spend ₹ 10, 20, 30 ...........

On 1^st 2^nd 3^rd ....... day respectively

ATQ

10 + 20 + 30 .............=18300

`"S"_"n"="n"/2(2"a"+("n"-1)"d")`

`"n"/2(2(10)+("n"-1)10)=18300`

`"n"/2[10"n"+10]=18300`

5n² + 5n = 18300

n² + n − 3660 = 0

n² + 61n − 60n − 3660 = 0

n (n + 61) − 60(n + 61) = 0

(n − 60) (n + 61) = 0, n = 60, n ≠ 61

n = 60
i.e. 2 months