# Numer Theory

posted by .

1+2+3+...+n=(1+n)+(2+(n-1))+(3+(n-2))+...
=(1+n)+(1+n)+(1+n)+...

How many copies of n+1 are in there in the second line?
with n=6 and n=7

• Number Theory -

Since the n numbers are divided up in pairs, I'd say n/2 copies.

Hence the formula for the sum: n(n+1)/2

Technically, that's [n+1]/2 where [] is the greatest-integer function.

## Similar Questions

1. ### math,correction,help

please can someone tell me where i am wrong. Directions: Translate to a system of equations and solve. Problem: Colored copies cost 10cents per copy and white copies cost 5cents per copy. Sandy made 400 copies, some of which were colored …
2. ### Math

At Kinko's, Sean made 56 copies costing \$16. Color copies cost \$0.75 each and black and white copies cost \$0.10 each. How many copies of each did Sean make?
3. ### math

The president of the country PTA organization makes copies of membership lists for all of the elementary schools. Sometimes she may need only few copies but at other times she needs thousands of copies. TIP copy Service charges 3 ½ …
4. ### math

The president of the country PTA organization makes copies of membership lists for all of the elementary schools. Sometimes she may need only few copies but at other times she needs thousands of copies. TIP copy Service charges 3 ½ …
5. ### Math

A copy machine makes 60 copies per minute. A second copy machine makes 80 copies per minute. The second machine starts making copies 2 minutes after the first machine starts. Both machines stop making copies 8 minutes after the first …
6. ### algebra1

the school bought a new copy machine which makes 20 copies per minute.the old machine makes 12 copies per minute.francine needs 100 copies,so she uses both machines.how long will it take to have the copies
7. ### algebra1

the school bought a new copy machine which makes 20 copies per minute.the old machine makes 12 copies per minute.francine needs 1000 copies,so she uses both machines.how long will it take to have the copies
8. ### Statistics

There is a mathematical theory called queuing theory that studies ways in which computer jobs are fed in CPUs and researches on how these can be reduced to a minimum. Show how can a computer estimate the average number of jobs waiting …
9. ### Math

School is planning to purchase a new copy machine. The principal has narrowed the choice to two models. Superfast Deluxe and Quick Copies. He plans to purchase the machine that copies the quickest rate. Use this info to determine which …
10. ### LA 1 QUESTION PLZ HELP ASAP

1)How many stressed syllables are in these lines?

More Similar Questions