Question 217487: What is the sum of the positive multiples of 13 that are less than 300? Found 2 solutions by rfer, MathTherapy:Answer by rfer(16322) (Show Source):
Since we’re looking for all multiples of 13 that are less than 300, we start at 13 (13 * 1) and end at 299 (300 / 13, and then round down). This means that the multiples begin at 13 and end at 299.
Now, since the least multiple is multiplied by 1, and the largest is multiplied by 23, then we’re going to have a total of 23 multiples (23 – 1 + 1).
The average of the series of numbers that we’re looking for is 156 (), and since the number of numbers in the series is 23, the sum of the positive multiples of 13 that are less than 300 = 156 * 23 =
(