Question

How many keys on a typewriter must be pressed to type the numbers from 1 to 100 without a space?

Answer 1

We know, there are 9 one digit numbers, 90 two digit numbers and 1 three digit number.

Keys pressed in one digit numbers=9*1=9

Keys pressed in two digit numbers=90*2=180

Keys pressed in three digit number=1*3=3

Total number of keys pressed=9+180+3=192

Therefore, typewriter must be pressed 192 keys.