Change resourceExample 7
Mathematics · Chapter 5 · NCERT Examples
Verified NCERT questions and solutionsSolutions are checked independently and follow the supplied NCERT chapter edition.
How many two-digit numbers are divisible by 3?
Solution
Board-exam working:
The first two-digit multiple of 3 is 12 and the last is 99, so the AP is 12,15,…,99 with a=12,d=3,l=99.
Use l=a+(n−1)d: 99=12+3(n−1).
Thus 87=3(n−1), n−1=29 and n=30.
Check: a₃₀=12+29×3=12+87=99.
