Question

The sum of all odd numbers form 1 to 99 is?

Answer 1

use sum of aritmetic sequence. .

Answer 2

1 + 3 + 5 + 7.....But you need not do that since it is an arithmetic sequence.

Answer 3

The sum of an arithmetic sequence is:

\(\Large \color{Black}{\Rightarrow {n \over 2}(a_1 + a_l) }\)

a1 is the first term
aL is the last
n is the number of terms

Answer 4

After 1 add? Should i cross multiply?

Answer 5

1st term is 1.
Last is 99.
Odd numbers between 1,100 are 50.

Answer 6

The common difference is d, btw.

Answer 7

@ParthKohli , i think you've mistaken the formula.

. http://www.regentsprep.org/Regents/math/algtrig/ATP2/ArithSeq.htm

Answer 8

Oops, it was aN lol

Answer 9

it's ok. .

Answer 10

I dont get it XD

Answer 11

Hey I know another pattern.

Answer 12

The sum of first n odd numbers is n squared.
The sum of first 50 odd numbers is 50 squared.
So, 50^2 = 2500

Answer 13

Well actually my formula was correct.

Answer 14

I learnt this pattern at school.

Answer 15

Ca you give me an example?

Answer 16

For example the sum of first 4 odd numbers is 4 squared aka 16
1 + 3 + 5 + 7 = 4 + 12 = 16

Answer 17

how did you got that formula? @ParthKohli

Answer 18

Oh wait a second

Answer 19

Yes....yes I'm correct.

Answer 20

the answer is 2500, and you're correct, but how did you get that another formula?

Answer 21

I learnt that at school

Answer 22

@sel126 Got it?

Answer 23

Yessss :) Thankyousomuch:)))))))

Answer 24

Yw :D

Answer 25

99 = a + (n-1)d
hence 99 = 1 +(n-1)*3
n= 50

substituting value of n in equation S= n/2 [ 2a + (n-1)*d]
we get sum of odd terms
that is equal to 2500

where a =1(first term) and d =3(common difference)

Answer 26

Why does three become the d?

Answer 27

the sum of odd numbers is a perfect square

Answer 28

That's what I said above

Answer 29

Hehe don't waste your energy, genius. I've explained her.

Answer 30

just thought i would mention it. no need for a formula, or all that other business, only need to know how many numbers are being added

Answer 31

Hmm I said the exact same thing.

Answer 32

Still here you have a medal