Question

2) In an AP, the first term is -5 and last term is 45.If sum of all numbers is 120, then how

many terms are there?





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Answer 1

Step-by-step explanation:

a=-5

l=45

Sn=120

Sn=n/2{2a+(n-1)d}

or

n/2(a+l)

120=n/2 (-5+45)

120=(n/2) (40)

120=20n

20n=120

n=120/20

n=6

so there is 6 terms

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