MCQ

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?

#### Options

1 month

2 months

3 months

4 months

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#### Solution

**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`

5n^{2} + 5n = 18300

n^{2} + n − 3660 = 0

n^{2} + 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

Concept: Series and Equations (Entrance Exam)

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