SOLUTION: A student wants to know how many integers between 1 and 1000 are a multiple of 3 or a multiple of 5. She wonders if it is correct to find the number of those integers that are mu

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Question 174107: A student wants to know how many integers between 1 and 1000 are a multiple of 3 or a multiple of 5. She wonders if it is correct to find the number of those integers that are multiples of 3 and add the number of those that are multiples of 5. How do you respond?
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
I would respond, < Buzzer Sound > "Sorry, wrong answer. Thank you for playing; we have some lovely parting gifts."

If you take the number of multiples of 3 between 1 and 1000 and add it to the number of multiples of 5 between 1 and 1000, your answer would be too large by the number of multiples of 15 because multiples of 15 are also multiples of 3 AND multiples of 5 and therefore would be double counted by the given method.

Hence, the correct method to determine the number of integers between 1 and 1000 that are a multiple of 3 or a multiple of 5 is to perform the following calculation:

M%5B3%5D%2BM%5B5%5D-M%5B15%5D where M%5Bn%5D is the number of multiples of n between 1 and 1000.