What are 8 numbers between 50 and 100 that are divisible by 3?

Answer 1

The first step is to find the first number divisible by 3. You can use a number of techniques, but I'll list the easiest.

3 does not divide 50 (i.e., 50/3 is not an integer, it's ~= 16.667)

3 divides 51 (i.e., 51/3 = 17, it's an integer)

So 51 is the first integer between 50 and 100 that is divisible by 3. From there we can simply add any multiple of 3 to 51 to return other integers which are divisible by 3. Or to put it in a function:

x = 51 + 3n, where n is some integer

If n=0: x = 51 + 3(0) = 51
If n=1: x = 51 + 3(1) = 54

To find the maximum value of n, that bounds the function between 50 and 100.

100 = 51 + 3n
100 - 51 = 3n
49 = 3n
49/3 = n

n = 49/3 ~= 16.3
since we only care about integers, we can state that n must be less than 16 to satisfy the our requirement:

n=16: x = 51 + 3(16) = 99

So here are all the possible answers you can pick from, choose any 8:

51, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 84, 87, 90, 93, 96, 99

To restate how to do this. Find the first number that is divisible by three between 50 and 100. Then keep adding 3 to it to produce new numbers until you reach your upper bounds (100).