Question

hiii!!!

find the sum :-

7 + 10½ + 14 + ··· + 84

plz don't spam!!

content quality required..

all the best :D

Answer 1

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Here is your solution in the pic. attached

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Answer 2

Hey !!

Thanks for the question.

Given,

a = 7

d = 10 1/2 - 7

= 7/2

an = a + ( n - 1 )d

= 7 + ( n - 1 ) 7/2

= 7 + ( 7/2 n - 7/2 )

84 = 7 + 7/2n - 7/2

84 = 7/2 + 7/2n

84 - 7/2 = 7/2 n

161/2 = 7/2 n

161/2 × 2/7 = n

n = 23

Sn = n/2 ( a + l )

= 23/2 ( 7 + 84 )

= 23/2 × 91

= 2093/2 

= 1046.5