Answer:
7
Step-by-step explanation:
You can estimate the number as being ...
(100 -50)/7 = 50/7 = 7 r 1
That is, there are likely to be 7 multiples of 7 between 50 and 100. This is a small enough number of them that we can count them:
56, 63, 70, 77, 84, 91, 98 . . . . 7 multiples of 7
_____
In general, you want to make sure that you don't overlook one at the beginning or end of the range. One way to ensure that you get a correct count is to write an equation for the n-th multiple of 7 in the range. Here, that would be 49+7n. We would want to find n such that ...
49 +7n ≤ 100
7n ≤ 51
n ≤ 51/7 = 7 2/7
The largest integer n less than 7 2/7 is 7, so there are 7 multiples of 7 between 50 and 100.
