Averages, weighted average, simple arithmetic mean problems : CAT MBA Entrance classes

Question 4 the day : June 11, 2004
The question for the day is from the topic average in arithmetic.

Question
The average wages of a worker during a fortnight comprising 15 consecutive working days was Rs.90 per day. During the first 7 days, his average wages was Rs.87/day and the average wages during the last 7 days was Rs.92 /day. What was his wage on the 8^th day?

1. 83
2. 92
3. 90
4. 97

Correct Answer - 97. Choice (4) is correct.

Explanatory Answer

The total wages earned during the 15 days that the worker worked = 15 * 90 = Rs. 1350.

The total wages earned during the first 7 days = 7 * 87 = Rs. 609.
The total wages earned during the last 7 days = 7 * 92 = Rs. 644.

Total wages earned during the 15 days = wages during first 7 days + wage on 8^th day + wages during the last 7 days.

ð     1350 = 609 + wage on 8^th day + 644
ð     wage on 8^th day = 1350 - 609 - 644 = Rs.97.

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