Mathematics · Arithmetic Progressions · NCERT Examples
Example 8
A complete, independently verified solution for NCERT Example 8.
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Mathematics · Chapter 5 · NCERT Examples
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NCERT Example
Example 8
Find the 11th term from the end of 10,7,4,…,−62.
Solution
Board-exam working:
Here a=10,d=−3,l=−62.
First find the number of terms: −62=10+(n−1)(−3)=13−3n.
Thus 3n=75 and n=25.
The 11th term from the end is term number 25−11+1=15 from the start.
a₁₅=10+(15−1)(−3)=10−42=−32.
Check from the end: −62+(11−1)3=−62+30=−32.
Final answer
−32.