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13 Mar 2016, 12:44
Kudos
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D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
81% (01:54) correct
19%
(01:51)
wrong
based on 166
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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 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
A. $83
B. $90
C. $92
D. $97
E. $104
13 Mar 2016, 19:37
Kudos
Bookmarks
Average daily wage of a worker for 15 consecutive working days = 90$
During the first 7 days , the daily average daily wage = 87$
During the last 7 days , the daily average daily wage = 92$
Wage on 8th day = 90*15 -( 87*7 + 92 *7)
= 1350 - (609 + 644)
=1350 - 1253
= 97
Answer D
Alternatively ,
During the first 7 days , since the daily average daily wage = 87$
Amount by which sum of first 7 days varies from average for entire 15 days = -3*7 = -21
During the last 7 days , since the daily average daily wage = 92$
Amount by which sum of last 7 days varies from average for entire 15 days = 2*7 = 14
Amount by which sums first 7 and last 7 days varies from average for entire 15 days = -21 +14 = -7
Therefore , in order to make average for entire 15 days to be 90 , the wage on 8th day needs to be = 90 + 7 = 97
Answer D
During the first 7 days , the daily average daily wage = 87$
During the last 7 days , the daily average daily wage = 92$
Wage on 8th day = 90*15 -( 87*7 + 92 *7)
= 1350 - (609 + 644)
=1350 - 1253
= 97
Answer D
Alternatively ,
During the first 7 days , since the daily average daily wage = 87$
Amount by which sum of first 7 days varies from average for entire 15 days = -3*7 = -21
During the last 7 days , since the daily average daily wage = 92$
Amount by which sum of last 7 days varies from average for entire 15 days = 2*7 = 14
Amount by which sums first 7 and last 7 days varies from average for entire 15 days = -21 +14 = -7
Therefore , in order to make average for entire 15 days to be 90 , the wage on 8th day needs to be = 90 + 7 = 97
Answer D
13 Mar 2016, 20:56
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Bunuel
Hi,
Ofcourse calculation of averages and subtraction etc here is not very cumbersome..
But another approach which cuts down on calculations and could help in some other Q of same type with cumbersome calculations..
Solution-
we are given averages for 7 days on either side..
the average of these 7+7 days can be easily found out as
92-87=5 so 5/2=2.5 from each number..
so average is 87+2.5= 89.5 for these 14 numbers..
15th number increases this by 90-89.5=0.5..
so 15th number= the final average + increase required in other 14 numbers= 90+14*(90-89.5)=90+14*0.5=90+7=97
