If we recongnize the expression given in the problem then we know its dealing wiht weighted average.
Rearrange the expression:
10x+20y/x+y
The average would be between 10 and 20 and hence 18 (since its given y>x therefore the average would be closer to 20 than 10. Hence we rule out 15 since its halfway between 10 and 20)
D)
NO idea
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logitech
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10x+20y / (x+y) = k
10x+10y / (x+y) + 10y /(x+y) = k
10 + 10y /(x+y) = k
10 [ 1 + y/(x+y)] = k
So it all comes down to what y/(x+y) could be. We know that y>x
Min: y=x
y/2y = 0.5
Max: x=0
y/y = 1
So k needs to be between:
10(1+0.5) < K < 10 ( 1+1)
15 < K < 20
Only 18 will fit into this range.
Choose (D)
10x+10y / (x+y) + 10y /(x+y) = k
10 + 10y /(x+y) = k
10 [ 1 + y/(x+y)] = k
So it all comes down to what y/(x+y) could be. We know that y>x
Min: y=x
y/2y = 0.5
Max: x=0
y/y = 1
So k needs to be between:
10(1+0.5) < K < 10 ( 1+1)
15 < K < 20
Only 18 will fit into this range.
Choose (D)
LGTCH
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