Mathematics · Arithmetic Progressions · NCERT Examples

Example 5

A complete, independently verified solution for NCERT Example 5.

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Mathematics · Chapter 5 · NCERT Examples

Verified NCERT questions and solutionsSolutions are checked independently and follow the supplied NCERT chapter edition.

NCERT Example

forming an AP

Determine the AP whose 3rd term is 5 and 7th term is 9.

Board-exam working:

a_n=a+(n-1)d

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.

3,4,5,6,7,…

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