Q. What is the number of fives used in numbering a 260-page book?

Explanation : 

To determine how many times the digit 5 appears in the page numbers of a 260-page book, we can analyze each digit place (units, tens, and hundreds) separately.

1. Units Place:

Every 10 numbers, the units digit cycles from 0 to 9.
Therefore, the digit 5 appears once in every set of 10 numbers.
Total sets of 10 in 260 pages: 260/10 = 26 sets.
Occurrences in units place: 26 × 1 = 26

2. Tens Place:

The digit 5 appears in the tens place for every number from 50-59, 150-159, and 250-259.
Each of these ranges contains 10 numbers where the tens digit is 5.
Total ranges with 5 in tens place: 3 (i.e., 50-59, 150-159, 250-259)
Occurrences in tens place: 3 × 10 = 30

3. Hundreds Place:

Since the book has only 260 pages, the hundreds digit can be 0, 1, or 2.
The digit 5 does not appear in the hundreds place within this range.
Occurrences in hundreds place: 0

Total Number of Fives:
Units place: 26
Tens place: 30
Hundreds place: 0
Total: 26 + 30 + 0 = 56

Therefore, the correct answer is b) 56.