GMAT® Practice Question - Averages

Concept: Computing average. Computing sum from average.

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.

Question: 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 8th day?

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

Explanatory Answer

Video explanation provided for this question

Fill in the data given in the question in the standard framework as shown below. 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.

Standard Framework
Description Number of days Average Wages Sum
All 15 days 15 $90 $1350
First 7 days 7 $87 $609
Last 7 days 7 $92 $644
14 days excluding 8th day     609 + 644 = $1253
8th day wage = Wages for all 15 - wages for 14 days excl 8th day     1350 - 1253 = $97

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

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

Total wages earned during the 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.

Video Explanation

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