Question

Calculate the following sum (100 values):
+ 11 13 15 ... 209

Answer 1

@Social
We have the series, let the sum be S
S=11+13+15..............+207+209

I can also write sum as
S=209+207.....+15+13+11

Do you follow this?

Answer 2

i know it

Answer 3

then? i do not remember

Answer 4

okay, then let's add the two series, we'll add term by term
11+209=220
13+207=220
15+205=220
so
we get
2S=220+220+220.....+220+220
Do you follow this?

Answer 5

yes

Answer 6

can you find the sum from here? it's just a step

Answer 7

11000

Answer 8

correct :) did you understand the solution?

Answer 9

yes... this is very clever
it means that i will have the same result with different numbers

Answer 10

many many years since school... i forgot them.. thank you!!

Answer 11

Welcome :D