Question

At a bus stop, Bus A arrives every 3 minutes, Bus B arrives every 4 minutes and Bus C arrives every 10 minutes. They start from bus stop right now. In how many minutes will they meet at the bus stop?

• A. 20 minutes
• B. 40 minutes
• C. 60 minutes
• D. 80 minutes

Answer 1

The correct option is C 60 minutes

The time taken for arrival at the bus stop is:
Bus A = 3 min
Bus B = 4 min
Bus C = 10 min

We have to find in how many minutes will all three buses meet again at the bus stop.

To do so, we need to find the lowest common multiple (LCM) of 3, 4 and 10 using ladder method.

So, let us write all 3 numbers on a horizontal line and divide these numbers using a prime number.


Write the quotients in the next line.

If the number is not exactly divided, write it in the next row along with the quotient of another number.

Repeat the process until the quotients are prime numbers.


Now, to obtain the LCM, we multiply all the divisors and the quotients in the last row.

So, LCM of 3, 4, 10 = 60

∴ All three buses will meet again at the bus stop after 60 minutes.