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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## The average wages of a worker during a fortnight... tagged by: swerve ##### This topic has 2 expert replies and 0 member replies ### Top Member ## The average wages of a worker during a fortnight... The average wages of a worker during a fortnight comprising 15 consecutives working days was$90 per day. During the first 7 days, his average wages was $87 per day and the average wages during the last 7 days was$92 per day. What was his wage on the 8th day?

A. $83 B.$90
C. $92 D.$97
E. $104 The OA is D. Please, can any expert explain this PS question for me? I have many difficulties to understand why that is the correct answer. Thanks. ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 10197 messages Followed by: 497 members Upvotes: 2867 GMAT Score: 800 Hi swerve, We're told that the average pay a worker received for 15 consecutives working days was$90 per day. During the first 7 days, his average wages was $87 per day and the average wages during the last 7 days was$92 per day. We're asked for his wage on the 8th day.

There are a number of different ways to approach the 'math' in this question. Here's an approach that allows you to avoid a lot of 'step-heavy' math and focus on the 'relationships' between the numbers.

Since the average pay was $90/day, we can track how much 'below average' or 'above average' the individual days are... -For the first 7 days, the average pay was$87/day, thus each of those days was $3 BELOW the average... meaning that we're (7)($3) = $21 'below' in total here. -For the last 7 days, the average pay was$92/day, thus each of those days was $2 ABOVE the average... meaning that we're (7)($2) = $14 'above' in total here. With those 14 days, we're a total of '$7 below' what the average is supposed to be, so that final day (the 8th day) has to make up for that difference...

8th day = $90 +$7 = $97 Final Answer: D GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com ### GMAT/MBA Expert GMAT Instructor Joined 04 Oct 2017 Posted: 551 messages Followed by: 11 members Upvotes: 180 Quote: The average wages of a worker during a fortnight comprising 15 consecutives working days was$90 per day. During the first 7 days, his average wages was $87 per day and the average wages during the last 7 days was$92 per day. What was his wage on the 8th day?

A. $83 B.$90
C. $92 D.$97
E. $104 The OA is D. Please, can any expert explain this PS question for me? I have many difficulties to understand why that is the correct answer. Thanks. Hi Swerve, Let's take a look at your question. The wages of a worker during a fortnight comprising 15 consecutive working days =$90 per day
We know that,
$$Average\ \ =\ \frac{Sum}{Days}$$
$$Sum\ =\ Average\ \times\ Days$$
$$Sum\ =\ 90\ \times15\ =\ 1350$$
Therefore,
Sum of wages of 15 days = $1350 Next the question states that During the first 7 days, his average wages was$87 per day.
Again using the average formula, we will find the sum of wages of first 7 days.
$$Average\ \ =\ \frac{Sum}{Days}$$
$$Sum\ =\ Average\ \times\ Days$$
$$Sum\ =\ 87\ \times7\ =\ 609$$
Therefore,
Sum of wages of first 7 days = $609 Next the question states that he average wages during the last 7 days was$92 per day.
Again using the average formula, we will find the sum of wages of last 7 days.
$$Average\ \ =\ \frac{Sum}{Days}$$
$$Sum\ =\ Average\ \times\ Days$$
$$Sum\ =\ 92\ \times7\ =\ 644$$
Therefore,
Sum of wages of last 7 days = $644 We need to find the wage on 8th day. We know that, Sum of wages of first 7 days + Wage on 8th day + Sum of wages of last 7 days = Sum of wages of 15 days Plugin in all the known wages we calculated above, 609 + Wage on 8th day + 644 = 1350 Wage on 8th day + 609 + 644 = 1350 Wage on 8th day + 1253 = 1350 Wage on 8th day = 1350 - 1253 Wage on 8th day = 97 The wage on 8th day is$97.

Therefore, Option D is true.

Hope it helps.
I am available if you'd like any follow up.

_________________
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