3. Consecutive odd numbers starting at 1 are added together. Their sum is 400. How many numbers were added?

Question

asked Nov 13, 2021 101k views

2 Answers

Layton · Answer 1 · 2021-11-18T23:04:24+0000

Answer:

20

Explanation:

Sn = (n/2)(a1 + a1 + d(n-1)), where S = sum, a1 = first term, n = number of terms, d = common difference

400 = (n/2)(1 + 1 + 2(n - 1))

400 = (n/2)(2 + 2n - 2)

400 = (n/2)(2n

400 = n2

20 = n

Twenty numbers are in the set.