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01 Sep 2016, 03:49
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D
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If the average (arithmetic mean) of x and y is 40, and z – x = 60, what is the average of y and z?
A. 20
B. 50
C. 65
D. 70
E. 140
A. 20
B. 50
C. 65
D. 70
E. 140
06 Sep 2016, 14:13
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Bunuel
If the average (arithmetic mean) of x and y is 40, and z – x = 60, what is the average of y and z?
A. 20
B. 50
C. 65
D. 70
E. 140
A. 20
B. 50
C. 65
D. 70
E. 140
Another approach is the assign values to x, y and z that satisfy the given conditions.
The average (arithmetic mean) of x and y is 40
Okay, two "nice" values are: x = 40 and y = 40
z – x = 60
Since we've let x = 40, then it must be the case that z = 100
What is the average of y and z?
If y = 40 and z = 100, then the average of y and z = (40+100)/2 = 70
Answer:
NOTE: there was nothing special about the values I chose for x, y and z, other than the fact that they satisfied the given conditions. ANY other set of numbers will also yield the same answer.
For example, we could have used x = 20, y = 60 and z = 80, and this would have led to the same answer.
Try your own values to confirm this.
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General Discussion
01 Sep 2016, 07:04
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Bookmarks
Bunuel
If the average (arithmetic mean) of x and y is 40, and z – x = 60, what is the average of y and z?
A. 20
B. 50
C. 65
D. 70
E. 140
A. 20
B. 50
C. 65
D. 70
E. 140
x+y/2 = 40
=> x+y = 80
x = z - 60...sub this value
z-60+y = 80
=>z+y = 140
=>z+y/2 = 70.
IMO option D.
OA please..will correct if I missed anything.
