Question

How many numbers between 100 and 999, inclusive, have 7 in the tens place?

Answer 1

Start with the 100s. How many numbers of the form 17x are there?

Answer 2

whatis answer?

Answer 3

How mane numbers of the form 17x are there?

Answer 4

I don't know

Answer 5

Well there's 170, 171, 172.... What else?

Answer 6

173

Answer 7

How many are there in the whole 17x range then?

Answer 8

1700

Answer 9

We're just counting the numbers from 170 up to 179. How many are there in that range?

Answer 10

ten

Answer 11

Correct. How many are of the form 27x then?

Answer 12

10

Answer 13

So add up all the 17x, 27x, 37x etc. What do you get?

Answer 14

9*10=90

Answer 15

Well done! That's the final answer.