Class 10 Math All topics Arithmetic Progressions

Find the sum of

$3+8+13+18+....+n$ terms

$3+8+13+18+....+n$ terms

Solution:

$3+8+13+18+.....$(n terms)

The given expression is an A.P.

first term $=a=3$

common difference$=d=5$

Sum of n terms$=S_{n}=2n [2a+(n−1)d]$

$=2n [2(3)+(n−1)5]$

$=2n [6+5n−5]$

$=2n [5n+1]$

$=25n_{2} +2n $.

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introduction to trigonometry

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quadratic equations

surface areas and volumes

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