Puzzles & Brain Teasers : Add Quickly - Worksheet / Test Paper

Math Puzzles & Brain Teasers

Add Quickly

Hide all answers Hide all answers View all answers View all answers Print Try the Quiz

Can you find a quick and elegant way to add the numbers from 1 to 46 ?

In other words, what is the sum you obtain in the following case:

1 + 2 + 3 + ....... + 46 =

Answer: 1081

Solution:

Here's an elegant way:

1 + 46 = 47
2 + 45 = 47
3 + 44 = 47
.....................
.....................
23 + 24 = 47

Adding the above equations gives

1 + 2 + 3 + ....... + 46 = 23 × 47 = 1081

Food for thought:

The general formula is:

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

Is the formula valid when n is an odd integer?

Try the Quiz : Puzzles & Brain Teasers : Add Quickly