Asked by ACB121

Using Gauss’ method find the following sum:

54 + 63 + 72 + . . . + 189 + 198 + 207
Answered by oobleck
(207-54)/9 = 17
so there are 18 terms.
That makes 9 pairs which add up to 54+107 = 161
9*161 = ___
Answered by mathhelper
sum = (18/2)(54+207) = 2349

confirming by using the sum formula (n/2)(2a + (n-1)d)
= (18/2)(108 + 17(9)) = 2349
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