Hello from MrBillDoesMath!
Answer:
225
Discussion:
Sum ( 2n - 1) from n = 1 to 15
= Sum(2n) - Sum(1) from n = 1 to 15
= 2 Sum(n) - Sum(1) from n = 1 to 15
= 2* 15(15+1)/2 - (1 + 1 + .. + 1)
The first value comes from the fact that the sum of the first n integers is n(n+1)/2. The latter value sums 15 1's.
= 2 * 15 * 16/2 - 15 => 2/2 = 1
= 15*16 - 15 => 15*16 = 240
= 240 - 15
= 225
Thank you,
MrB