Question

how many numbers are there between 99and1000 having 7 inthe units place

Answer 1

X
Find x
I will give u a clue
X-x is the numbers between 99 and 1000

Answer 2

Method: The least number possible here is 107 and maximum is 997. Just keep on adding +10 to 107 till you reach 997.

Solution:

Here we have locked the unit place to 7. The only freedom you have is to change the 10s and 100s places. It is simply the difference between the first two digits of either numbers (i.e., 997 and 107). So,

99-10=89. Now add 1 to account for the first number (107). i.e., 89+1=90 such numbers.