16. To the nearest second, what is the first time after 7 that the hand of a clock form a right angle?
The ansewr is 7:22:35.
90=abs((30*7) - (5.5*M)), solve for M
M==240 / 11 ==21.818181.........etc. minutes after 7:00 O'clock.
90 degrees==7:21.818181...........etc.
