How many times will it flash??

If a light flashes every 6 seconds, how many times will it flash in 3/4of an hour?

Answer: 

451 times.

Explanation:

There are 60 minutes in an hour.

            In ¾ of an hour there are (60 * ¾) minutes  = 45 minutes.

                        In ¾ of an hour there are (60 * 45) seconds = 2700 seconds.

            Light flashed for every 6 seconds.

                        In 2700 seconds 2700/6 = 450 times.

The count start after the first flash, the light will flashes 451 times in ¾ of an hour.