Answer:
[tex]Time = 11\frac{2}{3}\ min[/tex]
Step-by-step explanation:
Given
[tex]Security\ A = 2\ mins, 20\ secs[/tex]
[tex]Security\ B = 1\ mins, 40\ secs[/tex]
Required
After how many minutes, will they round together
First, convert the given time to minutes
[tex]Security\ A = 2\ mins, 20\ secs[/tex]
[tex]Security\ A = 2\ mins+ 20\ secs[/tex]
[tex]Security\ A = 2\ mins+ \frac{20}{60}\ min[/tex]
[tex]Security\ A = 2\ mins+ \frac{1}{3}\ min[/tex]
[tex]Security\ A = 2\frac{1}{3}\ min[/tex]
[tex]Security\ B = 1\ mins, 40\ secs[/tex]
[tex]Security\ B = 1\ mins+ 40\ secs[/tex]
[tex]Security\ B = 1\ mins+ \frac{40}{60}\ min[/tex]
[tex]Security\ B = 1\frac{2}{3}\ min[/tex]
So, we have:
[tex]Security\ A = 2\frac{1}{3}\ min[/tex]
[tex]Security\ B = 1\frac{2}{3}\ min[/tex]
List out the multiples of the time of both security personnel take round.
[tex]Security\ A = 2\frac{1}{3}min,\ 4\frac{2}{3}min,\ 7min,\ 9\frac{1}{3}min,\ 11\frac{2}{3}min...[/tex]
[tex]Security\ B = 1\frac{2}{3}min,\ 3\frac{1}{3}min,\ 5min,\ 6\frac{2}{3}min,\ 8\frac{1}{3}min,\ 10min\ ,11\frac{2}{3}min,...[/tex]
In the above lists, the common time is:
[tex]Time = 11\frac{2}{3}\ min[/tex]
This implies that they go on round after [tex]11\frac{2}{3}\ min[/tex]
