Find the sum of first 20 terms of an A.P. whose n^{th} term is given as a_n = 5 - 2n.... | VSA 2m | Maths | SuperPadhai

Arithmetic Progressions > Question

VSA2 marksYear: 2022EasyCBSE Class 10

arithmetic-progressionssum-of-termsnth-term

Question

Find the sum of first

20

terms of an A.P. whose

n^{t h}

term is given as

a_{n} = 5 - 2 n

.

Solution

1

a_{1} = 5 - 2 = 3

+0.5 marks

2

a_{20} = 5 - 40 = - 35

+0.5 marks

3

S_{20} = \frac{20}{2} (3 + (- 35)) = 10 \times (- 32) = - 320

+1 mark

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