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.
