SOLUTION: Between the times 830 am and 3:30 pm, how many times will the hour and minute hands form a right angle on a clock face? Between the times 830 am and 3:30 pm, how many times

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Question 946442: Between the times 830 am and 3:30 pm, how many times will the hour and minute hands form a right angle on a clock face?


Between the times 830 am and 3:30 pm, how many times will the hour and minute hands form a right angle on a clock face?

a. 2
b. 5
c. 11
d. 12

My answer is a but in the book answer is d.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Assume the big hand only moves on the hour.
So at 9:00, they would be at right angles, at 9:30.
10:05 and 10:35
11:10 and 11:40
12:15 and 12:45
1:20 and 1:50
2:25 and 2:55
That makes the 12 times.
.
.
If the big hand moves with the hour, then the timing is off by a little.
9:00 would still be good but it might be 9:32 until it happens again, and so on.