There are

10,000/2 = 5,000

of such pairs. Each pair adds up to

(10,000 + 1)=10,001

The answer is

5,000 (10,000 + 1) = 50,005,000

This series represents the sum of an arithmetic progression with the first term 1 and common difference. The general formula for the sum of n consecutive natural numbers is:

S(n) = n(n+1)/2

1+2+3+4+5+6+7+8+9+10+1+2+3+4+5+6+7+8+9+10

and so on.

hes probably just adding by tens

S means the sum. n is the number of terms (which in this case is 10,000). a is the first term, which is 1. an the last term which is 10,000. So if you plug in all the info it will give you something like this:

S=10,000(1+10,000)/2= 50,005,000 if my math is correct.

1+10,000=10,001

now take the 2nd number, and the 2nd to last number…

2+9999=10,001

see a pattern? yup, there’s a pattern.

10,001 * 5,000 = 50,005,000

10000 +(1+9999)+(2+9998)… etc

how many groups that equal 10000