Mixed Operation Pyramids: Every brick has its own operation: add, subtract or multiply. Work backwards with the inverse. This is one of the many kinds of math pyramid we make, and here is how it works, with a video, a worked sample and a pyramid you can try right on this page.
The rule
Each brick is made from the two bricks under it with the operation shown on it: the left brick, then the operation, then the right brick.
A worked sample
Undo the minus
The top brick is left − right: 6 = 12 − ?. To undo a take-away, take the answer from the left brick: ? = 12 − 6 = 6.
Undo the times
The left brick of row 2 is 3 × ? = 12. To undo a times, divide: ? = 12 ÷ 3 = 4.
Check the plus
The last brick should be 4 + 2 = 6, and it is. Every operation agrees, so the pyramid is solved, and it is the only answer.
Your turn
Try it: undo the operations
Each brick shows its operation. Work backwards from the numbers you can see, then press Check.
Why it is worth doing
Because each brick has its own operation, you cannot just add. You have to decide which inverse undoes it, which is the heart of back-solving.
Books mentioned
Mixed Operation Math Pyramids
124 pyramids that add, subtract and multiply, for teens and adults. Full solutions are in the back.
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