2J homework 24.3.16

We have been playing this game this week; have a go over the weekend with your parents or brothers and sisters. 

Secret Number

Stage: 1  

This is a game for two players and a simple calculator.

Annie and Ben are playing. Annie puts her secret number into the calculator without showing Ben.

Annie then asks Ben, "What do you want to add?"

Ben tells Annie the number he wants to add. "I want to add four."

Annie presses the 'add' button and then the four button. The calculator now shows '4'. Annie gives the calculator to Ben.

Ben presses the 'equals' button and the calculator gives the answer '10'.

What was Annie's secret number?
How do you know?
You could play this with a friend. If you work out your friend's secret number correctly, it is your turn to put in a secret number of your own. You could score a point for every one you get right.