Browse Teasers
Search Teasers

## 30 Numbers

Math brain teasers require computations to solve.

 Puzzle ID: #48749 Fun: (2.75) Difficulty: (2.04) Category: Math Submitted By: shenqiang Corrected By: topnotch54

Numbers from 1 to 30 are written on a blackboard.

Add the first two numbers, and append it to the end, then erase the first two numbers.

For example, after the first time, the numbers become 3, 4, 5, ..., 29, 30, and 3.

Repeat this process until you get only one number.

How many addition operations are there, and what is the last number on the blackboard?

## What Next?

See another brain teaser just like this one...

Or, just get a random brain teaser

If you become a registered user you can vote on this brain teaser, keep track of
which ones you have seen, and even make your own.

 averageguy May 27, 2011 from 30 terms it will go to 15 terms, and then to 8 terms, and then 4 terms and then to 2 terms, ultimately, there will only be 1 term. like this puzzle!!!!! averageguy May 27, 2011 you can express a new number as the sums of the previous ones and you'll eventually be left with the two numbers 137 and 328 or, (1+2+3+4+21+22+23+24+25+26+27+28+29+30) and (5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20) respectively, you'll then add these last 2 numbers and notice that you've just added the numbers 1-30. pating May 31, 2011 Nice teaser. Different from those I already read. SRB_1807 Aug 16, 2011 Really Good one..