Question

What is the sum of a 10–term arithmetic sequence where the first term is 3 and the last term is 75?

Answer 1

A = {3+...+7}
+A = {7+...+3}
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2A = {10+...+10}

2A = 10*10 = 100

A = 100/2 = 50

Answer 2

opps, last term is 75 not 7 :)

Answer 3

same idea tho

(75+3)10/2

78*5