Q. What is the number of fives used in numbering a 260-page book?
a) 55
b) 56
c) 57
d) 60
Correct answer: b) 56
Question from UPSC Prelims 2024 CSAT Paper
Explanation:
Number of fives in 260-page book
To count the fives in a 260-page book:
1. Last digit (ones place):
– Appears every 10 pages: 5, 15, 25, …, 255
– Count: 26 times
2. Middle digit (tens place):
– Appears in 50-59, 150-159, 250-259
– Count: 3 sets of 10 = 30 times
3. First digit (hundreds place):
– Never appears (book doesn’t reach 500)
– Count: 0 times
Total count of fives: 26 + 30 + 0 = 56