Mathematics · Arithmetic Progressions · NCERT Examples
Example 10
A complete, independently verified solution for NCERT Example 10.
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Mathematics · Chapter 5 · NCERT Examples
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NCERT Example
Example 10
Rows of a flower bed contain 23,21,19,…,5 rose plants. Find the number of rows.
Solution
Board-exam working:
The row counts form an AP with a=23,d=21−23=−2 and last term l=5.
Use l=a+(n−1)d: 5=23+(n−1)(−2)=23−2n+2=25−2n.
Thus 2n=20 and n=10.
Check: a₁₀=23+9(−2)=23−18=5.
Final answer
10 rows.