Mathematics · Chapter 5 · NCERT Examples
Verified NCERT questions and solutionsSolutions are checked independently and follow the supplied NCERT chapter edition.
Determine the AP whose 3rd term is 5 and 7th term is 9.
Solution
Board-exam working:
a₃=a+2d=5 and a₇=a+6d=9.
Subtract the first equation from the second: (a+6d)−(a+2d)=9−5, so 4d=4 and d=1.
Substitute d=1 in a+2d=5: a+2=5, so a=3.
Therefore the AP begins 3,4,5,6,7,…
its third and seventh terms are 5 and 9.