Question

A grocer buys food from three suppliers. The suppliers deliver every 5 days, 6 days, and 7 days. All three came today. In how many days will they all deliver on the same day again?

Answer 1

210

Explanation:

For getting this answer we need to find the minimum common multiplier, this is, the smaller number that is multiple of all 5, 6 and 7.

For example, 30 is multiple of both 5 and 6, son in 30 days two suppliers will come, but not the third, as 30 is not a multiple of 7.

Let's try with the next multiple of 5 and 6, this is 60, but is not a multiple of 7.

The next is 90, but again not multiple of 7. Niether are the next: 120, 150, 180.

But when we arrive to 210 we see that, as we are going from multiples of 5 and 6, and 210/7=30, 210 is also multiple of 7.

So, the answer is 210.