Every 10 customers receive a soda. Every 9 customers receive a hot dog. There are 450 customers. How

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Every 10 customers receive a soda. Every 9 customers receive a hot dog. There are 450 customers. How many received both a soda and hot dog?

Fine the Least Common Multiple of 9 and 10 using our LCM Calculator:
LCM(9, 10) = 90. So every 90 customers receives a soda and a hot dog.
We have 90, 180, 270, 360, 450, so 5 customers receive both.