# Decimal Calculator Numbers

Purpose

The purpose of this activity is to work out a hidden number on a calculator using knowledge of number sequence.

Achievement Objectives
NA4-6: Know the relative size and place value structure of positive and negative integers and decimals to three places.
Specific Learning Outcomes

use their knowledge of decimal number sequence order decimals.

Required Resource Materials
One calculator per person.
Activity
1. Students enter a number into their calculator and push the division sign once. The student keeps pressing the equals sign until 0 is shown (depending on the ability of the student you could allow a one, two, three, or four decimal place number).
2. The student then hands over their calculator to a partner. It is important that no other button is pressed on the calculator as it is handed over.
3. The partner puts in a number and presses =. Again it is imperative that no other number is pressed as this will wipe the memory on the calculator.
4. The number displayed on the calculator screen will tell the partner how close they are to the number entered. A number larger than 1 means the number they entered is bigger than the mystery number and a number less than 1 means the number is smaller than the mystery number.
5. The partner can keep trying numbers, thinking about whether they need a smaller or larger number each time.
6. The challenge is to get 1 displayed on the screen in as few guesses as possible. Once the partner has a 1 displayed on the screen they have guessed the mystery number.