Question

After every 3 days, Alex has a chocolate milkshake, and after every 4 days, he has a strawberry milkshake. On what all dates (in the same month) will he have both of those together, if he had them on 1st of December?​

Answer 1

Alex has a chocolate milkshake every 3 days, while a strawberry milkshake every 4 days.

We have given that on the 1st of December he had them both.

We have to check on which days he will have both of the milkshakes.
Let’s check all the days on which he will have the chocolate and strawberry milkshakes by using the concept of common multiples of 3 and 4.


We have only written multiples till 31 as the month of December has only 31 days.
Let’s check the common days now. The numbers written in the space common to both the circles are the common multiples of 3 and 4.
So, the common days are 12, and 24.
Thus, after 12 and 24 days from the 1st of December Alex will have both chocolate and strawberry milkshakes.
Hence, the dates on which he will have both the milkshakes will be: 1st December, 13th December, and 25th December.