suppose a number from 1 to 100 is selected at random. what is the probability that a multiple of 4 or 5 is chosen?

Question

anonymous · Answer

First count up all the multiples of 4 or 5:

4, 5, 8, 10, 12, 15, 16, 20, 24, 25, 28, 30, 32, 35, 36, 40, 44, 45, 48, 50, 52, 55, 56, 60, 64, 65, 68, 70, 72, 75, 76, 80, 84, 85, 88, 90, 92, 95, 96, 100, 

There are 40 of these, so the probability is: $$\frac{40}{100} = \frac{2}{5}$$ or $$0.4$$ or

40%

$$ P(x|1<x<100;xmod4=0 OR xmod5=0) = 0.4$$

anonymous · Answer

ohhh thank you so much!! I was so confused.

anonymous · Answer

No problem.