Question

Security A rounds every 2 minutes and 20 seconds in the gate 1. Security B rounds every 1 minute and 40 seconds in the gate 2. If they conduct rounds at the same time. After how many minutes they will rounds together again?

Answer 1

Answer:

$Time = 11\frac{2}{3}\ min$

Step-by-step explanation:

Given

$Security\ A = 2\ mins, 20\ secs$

$Security\ B = 1\ mins, 40\ secs$

Required

After how many minutes, will they round together

First, convert the given time to minutes

$Security\ A = 2\ mins, 20\ secs$

$Security\ A = 2\ mins+ 20\ secs$

$Security\ A = 2\ mins+ \frac{20}{60}\ min$

$Security\ A = 2\ mins+ \frac{1}{3}\ min$

$Security\ A = 2\frac{1}{3}\ min$

$Security\ B = 1\ mins, 40\ secs$

$Security\ B = 1\ mins+ 40\ secs$

$Security\ B = 1\ mins+ \frac{40}{60}\ min$

$Security\ B = 1\frac{2}{3}\ min$

So, we have:

$Security\ A = 2\frac{1}{3}\ min$

$Security\ B = 1\frac{2}{3}\ min$

List out the multiples of the time of both security personnel take round.

$Security\ A = 2\frac{1}{3}min,\ 4\frac{2}{3}min,\ 7min,\ 9\frac{1}{3}min,\ 11\frac{2}{3}min...$

$Security\ B = 1\frac{2}{3}min,\ 3\frac{1}{3}min,\ 5min,\ 6\frac{2}{3}min,\ 8\frac{1}{3}min,\ 10min\ ,11\frac{2}{3}min,...$

In the above lists, the common time is:

$Time = 11\frac{2}{3}\ min$

This implies that they go on round after $11\frac{2}{3}\ min$