Number Pyramids: Addition Puzzles with Negatives, Decimals and Algebra
Number pyramids: each brick is the sum of the two below it, some bricks are given, and you find the rest. Whole numbers to start, then negatives, decimals, and algebra bricks like 2x + 3 for Higher. Play solo and each brick is marked the moment you press Enter, or put a pyramid on the board for a class and reveal it one brick at a time. Fresh pyramids every run, and no sign-up. Teachers: the menu at the top has the other starters, and Copy link for your class sends the solo version out.
Type each answer and it is marked as you go.
Choose a deck
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Ready when you are
Blast in progress
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Send the class this deck to play on their own, marked as they go.
Mark together
How number pyramids work
Every brick is the sum of the two bricks directly under it. When both bricks below are known, add them; when the brick above and the brick beside are known, subtract to find the one that is missing. Every pyramid here can be finished one brick at a time in that way, so there is always a next brick to find and never a pair of simultaneous equations to solve, and the reveal on the board fills the bricks in exactly that order.
Three, four or five rows. Whole numbers first; negative numbers make the subtraction bite; decimals to one place keep the place value honest; and algebra bricks add by collecting like terms, so a pyramid whose bottom row is 2x + 3, x, and 3x has 3x + 3 and 4x above them and 7x + 3 at the top. A brick's answer in the algebra pyramid has to be in its simplest form, as it would in an exam.
Running it as a maths starter on the board
Switch to Projector, choose the bricks and the rows, and press Start: the pyramid fills the screen with the clock, the class copies it and fills it in on paper, and when the time is up Enter reveals the next brick, in an order the class could have found it, until the pyramid is complete. Three pyramids at a minute each is a five-minute starter, and the answers screen lists every pyramid solved so the class can check theirs. The squares on the console are the same grid as the site's printed squared paper, which is the right paper to do these on.
The other maths starters
The menu at the top of the console groups the starters the way a teacher thinks of them: mental arithmetic (the Mental Maths Blast, the relay, Countdown, which is bigger, estimate it) and reasoning and puzzles (this page, spot the mistake, four in a row). Every one runs solo or on the board, and nothing about anyone is stored: a personal best stays in your own browser. The topic pages on IGCSE maths practice by topic have the practice rooms these starters are built from.