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Home » The sum of the first 9 terms of an AP is 81 and that of its first 20 terms is 400. Find the first term and common difference of the AP.
The sum of the first 9 terms of an AP is 81 and that of its first 20 terms is 400. Find the first term and common difference of the AP.
Arithmetic Progression | CBSE | Class 10 | Maths | RS Aggarwal
The sum of the first 9 terms of an AP is 81 and that of its first 20 terms is 400. Find the first term and common difference of the AP.

Solution:

Suppose the first term is a and d is the common difference in an AP, then we have:

i

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