Content

[hide]

## Problem – Math Game (AMC UP – 15)

*Sally thinks of a number, multiplies it by 2, adds 2, divides by 2 and then subtracts 2. Her answer is 2. What was her original number? *

- 1
- 2
- 3
- 5

**Key Concepts**

*Math Game*

*Arithmetic*

*Missing Number*

## Check the Answer

But try the problem first…

*Answer: 3*

Source

Suggested Reading

*Australian Mathematics Competition Upper Primary*

* 2014 UP 15*

*Secrets of Mental Math – Arthur T. Benjamin*

## Try with Hints

First Hint

*This sum is a tricky one. You can play game with this sum too*

*First we can start with a diagram where the number by which we are starting is X (assume).*

Final Hint

*In Hint 1 its clear that how to solve this problem.Try this ….*

*But if you really want a final hint then we have to solve it in reverse.Lets See another picture.*

*So the answer is 3.*

## Other useful links

- https://www.cheenta.com/missing-numbers-australian-mathematics-competition/
- https://www.youtube.com/watch?v=1O-BxsyPw6E&t=52s