| A blue light flashes 3 times per minute and a yellow light flashes 5 times in every two minutes. If both lights starts flashing at the same time, how many times do they flash together in each hours? |
A) 30
B) 40
C) 50
D) 60
Correct Answer: A
Solution :
(a)| Blue light flashes 3 times per min \[=\frac{60}{3}=20\] | |
| Blue light flashes after every 20 s. | ... (i) |
| Yellow light flashes 5 times every two minutes | |
| \[=\frac{2\times 60}{5}=24\,\,s\] | |
| \[\therefore \]Yellow light flashes every 24 s. | ... (ii) |
| So, both of them will flash together every 120 S. | |
| \[\therefore \]Number of times they flash together in 1 h | |
| \[=\frac{60\times 60}{120}=30\] | |
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