Asked by ACB121
Using Gauss’ method find the following sum:
54 + 63 + 72 + . . . + 189 + 198 + 207
54 + 63 + 72 + . . . + 189 + 198 + 207
Answers
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 = ___
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
confirming by using the sum formula (n/2)(2a + (n-1)d)
= (18/2)(108 + 17(9)) = 2349