Math Game - Australian Mathematics Competition, 2014

Content

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?

Math Game

Arithmetic

Missing Number

But try the problem first…

Answer: 3

Source

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.