What is the sum of the arithmetic sequence 152, 138, 124, ..., if there are 24 terms?

Hello:

124-138=138-152 = - 14 (common diference)

the sum of 24 terms is : S = n/2 (U1 + U 24)

n = 24 U1 = 152

Un = U1 + (n-1) d ... d = - 14

n=24 : U24 = 152 + (24-1) (-14) = 152-322 = - 170

S = 24/2 (152-170) = 12 (-18) = - 216

(24/2) {2 (152) + (24-1) (-14) } = - 216. - 216 is the sum of the sequence.