shapla wrote:

For each month of a given year except December, a worker earned the same monthly salary and donated one-tenth of that salary to charity. In December, the worker earned N times his usual monthly salary and donated one-fifth of his earnings to charity. If the worker's charitable contributions totaled one-eighth of his earnings for the entire year, what is the value of N?

A) 8/5

B) 5/2

C) 3

D) 11/3

E) 4

We can let the normal salary = k, so his total salary for the first 11 months was 11k. Each month k/10 went to charity, so for the first 11 months, his total charitable contribution was 11k/10.

The December salary was kN, and kN/5 was donated to charity.

Since the worker's charitable contributions totaled one-eighth of his earnings for the entire year:

kN/5 + 11k/10 = (kN + 11k)/8

Multiplying the equation by 40, we have:

8kN + 44k = 5kN + 55k

Dividing the equation by k, we have:

8N + 44 = 5N + 55

3N = 11

N = 11/3

Answer: D

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