Question

Qn 80: what is the total number of digits printed, if a book containing 150 pages is to numbered from 1 to 150?

Answer 1

There are 9 single digit ........... 9
90 double digit numbers...….......... +90×2
and 51 three digit numbers............ + 51×3
= 341

hope it helps

Answer 2

lets do it serial wise
one digit number
A =1-9 = total. number = 9

Two digit number
B = 10-99 = 90
since one value has two digits so 90 values has 2(90)

Three digit numbers
C = 100 - 150 = 51
since one value has 3 digits so 51 values has 3(51) digits.

so total number of digits will be

A + B + C
9 + 2(90) + 3(51)
9 + 180 + 153
= 342

so total digits will be 342.