GMAT Maths | GMAT Statistics Question 4

This GMAT quant practice question is a problem solving question in Descriptive Statistics. Concept: Compute the average for a set and parts of the set to determine the value of one element of the set. An easy to medium level difficulty question. A GMAT 600 level math sample question.

Question 4: The average wages of a worker during a fortnight comprising 15 consecutive working days was $90 per day. During the first 7 days, his average wages was $87/day and the average wages during the last 7 days was $92 /day. What was his wage on the 8^th day?

1. $83
2. $92
3. $90
4. $97
5. $104

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Video Explanation

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Explanatory Answer

Standard Framework

Description	Number	Average	Sum
All 15 days	15	$90	$1350
First 7 days	7	$87	$609
Last 7 days	7	$92	$644
14 days except 8th day			609 + 644 = $1253
8th day wage			1350 - 1253 = $97

Fill in the data given in the question in the standard framework as shown above. Most questions in averages can be solved by completing this standard framework. The sum of wages is computed as the product of the number of days and the average wage earned per day.

The sum of wages earned during the 15 days that the worker worked = 15 × 90 = $1350.

The sum of wages earned during the first 7 days = 7 × 87 = $609.
The sum of wages earned during the last 7 days = 7 × 92 = $644.

Sum of wages earned for all 15 days = wages during first 7 days + wage on 8th day + wages during the last 7 days.
Or, 1350 = 609 + wage on 8th day + 644
Wage on 8th day = 1350 - 609 - 644 = $97.

Choice D is the correct answer.