Respuesta :

dabicvietboi
Here is a trick that not a lot of people know

(# of terms)*(first+last)/2
(in case you don't know, * means multiply and / means divide)


abidemiokin

Answer:

679

Step-by-step explanation:

The formula for calculating the sum of an arithmetic progression which contains the first and the last term is expressed as;

Sn = n/2(a+l) where:

n is the number of terms in the series

a is the first term of the series

l is the last term of the series.

Given the series 3+10+......+87+94 which has 14terms,

a = 3

n = 14

l = 94

S3 = 14/2(3+94)

S3 = 7(97)

S3 = 679

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