naveendevaraj wrote:
The figure above shows two lines intersecting at the point O. If the lines are rotated about
O at the same rate and in the directions shown until AB is perpendicular to CD , through how many degrees
must each line move ?
A) 90 -Θ
b) 90 -Θ/2
C) 90 +Θ/2
d) (90+Θ)/2
e) (90+2Θ)/2
Explanations are welcomed.Thank you
Answer :
D
Plug in Θ = 10.
Since the lines are rotating toward each other, in order to become perpendicular, they must cover the 10 degrees between them and then rotate 90 degrees more: 10+90 = 100 degrees.
So each line must rotate 100/2 = 50 degrees. This is our target answer.
Now we plug Θ=10 into all the answers to see which gives us our target of 50.
Only answer choice D works:
(90+Θ)/2 = (90+10)/2 = 50.
The correct answer is D.
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