I'm having problems understanding these two questions.

28. If 6 and 14 are factors of y, must y be divisible by 21?

29. If 7y is a multiple of of 210, must y be a multiple of 12?

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- The MonicaA374
- Course Students
**Posts:**2**Joined:**Sun Sep 24, 2017 10:10 am

I'm having problems understanding these two questions.

28. If 6 and 14 are factors of y, must y be divisible by 21?

29. If 7y is a multiple of of 210, must y be a multiple of 12?

28. If 6 and 14 are factors of y, must y be divisible by 21?

29. If 7y is a multiple of of 210, must y be a multiple of 12?

- Sage Pearce-Higgins
- ManhattanGMAT Staff
**Posts:**943**Joined:**Thu Apr 03, 2014 4:04 am

You may find the Foundations of Math Workshop I a useful resource to watch. However, in short, "divisible by 2" means the same as "has a '2' among its prime factors". We can apply the same idea to question 28 and say that, since 6 and 14 are factors of y, y must have a '2', a '3', and a '7' among its prime factors. Now, any number that has a '3', and a '7' among its prime factors is divisible by 21.

Also check out the Divisibility chapter in the Foundations of Math book.

Also check out the Divisibility chapter in the Foundations of Math book.

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