Question

how many numers between 1-300 are divisble by 3 but not 5 and 7?

Answer 1

Nevermind, didn't read the question in full. Someone else has got to answer it :)

Answer 2

i would do this by elimination.

first there are 100 numbers divisible by 3

next we want to eliminate those that are divisible by 5
5*3 = 15 ---> those numbers must be multiples of 15
300/15 = 20 --> 100 - 20 = 80

now we want to eliminate numbers also divisible by 7
7*3 = 21 --> numbers must be multiples of 21
300/21 rounds down to 14 ---> 80 - 14 = 66

Finally we have to find any numbers which have double counted, divisible by both 5 and 7
3*5*7 = 105 --> these must be multiples of 105
300/105 rounds down to 2 ----> 66 + 2 = 68

There are 68 numbers between 1-300 that are divisible by 3 but not 5 or 7

Answer 3

Thanks alot for solving the Problem