
SILO 2.4 (DRAFT) Year 2, Term 4: Algorithms Focus: Algorithms Scope and sequence: Algorithms
Learning intention: Students explore number patterns as an introduction to algorithms.
NSW Syllabus	Australian Curriculum (version 9.0)
"A student describes, follows and represents algorithms to solve problems." (ST1-3DP-T)	"Students learn to recognise, describe and create additive patterns that increase or decrease by a constant amount, using numbers, shapes and objects, and identify missing elements in the pattern." (AC9M2A01)

Introduction to the topic

An algorithm is a set of steps used to complete a specific task. Although this word is often used in relation to technology, it can have a wider application in every day use. For example, an algorithm for preparing to go home at the end of a school day would involve packing up, clearing desks, and so on. The following video (2:30) provides an excellent overview of algorithms.

Number guessing game

The teacher chooses a secret number between 1 and 100 and writes it on the board before covering it over to conceal the number.
Students have 7 guesses to discover the number.
The teacher can only give "Yes" or "No" answers.
Reminders are written on the board to narrow down the options (e.g., if a students asked "Is it odd?" and the answer was "No", the teacher would write "Even" on the board.
Guesses are tallied up on the board and the answer is revealed after the seventh guess unless guessed earlier.

The game is played again with a student running the game.

The next stage with this activity is to contrast good guesses such as "Is it lower than 50?" with random guesses such as "Is it 87?" This can then be used as an introduction to algorithms where the aim is to narrow down the options. This is also a good way to introduce the word 'strategy'. A useful website for playing this game is https://toytheater.com/hundreds-chart/. On this site you can eliminate the numbers which have been ruled out using different colours. For example, the mystery number was 14 and the yellow shading was in response to the question, "Is it bigger than 50?". The blue shading was in response to the question, "Is it even?"

Number activity

Students choose a number between 1 and 100 and write it in a box in the middle of a sheet of paper (e.g., "25")
Students think of different ways to get this number and write them all over the page (e.g., 10 + 15; 5 x 5, 20 + 5, 30 - 5, 10 + 10 + 2 + 3, and so on).