Question

In an Ap the first term is -8 and the last term is 100 ​

Answer 1

correct question:-

In an AP if the first term is -8 and its last term is 100 then find its sum.

Given:-

• a = -8
• l = 100

to find:-

• sum of this AP

Formula:-

$\underline{\boxed{\sf \dfrac{n}{2}×(a+l) }}$

Solution:-

→ Sₙ = $\sf\dfrac{n}{2}×(a+l)$

→ Sₙ = $\sf\dfrac{n}{2}×(-8+100)$

→ Sₙ = $\sf\dfrac{92}{2}$

→ Sₙ = $\sf 46$

hence, the sum of the terms this ap = 46

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Additional Info.

to find nth term following formula is used:-

→ aₙ = a+(n-1)d

to find sum of the terms of A.P whose last term is not given

→ Sₙ = $\dfrac{n}{2}×2a+(n-1)d$