Every 3 days seth goes to the grocery store. his best friend brian goes every 5 days. on what day will they both go to the store on the same day?

The correct answer is:

The 15th day.

Explanation:

To answer this question, we must find the LCM (least common multiple) of these two numbers.

To do this, we find the prime factorization of each number:

3 = 3(1)

5 = 5(1)

The LCM is the common factors multiplied by the uncommon factors.  The only common factor we have is 1; the uncommon are 3 and 5:

1(3)(5) = 15

The 15th day they will go to the store on the same day.

step-by-step explanation: