Concept 5 of 5
Number Pyramids
Today's big idea
Top equals the two below
3 + 6 = 9; 9 − 3 = 6.
How it works
👀 What's going on?
Stack bricks so that each one rests on two others and shows their total. Build up or work down, and a number pyramid always keeps its promise: top equals the two below.
💡 Here's the trick
Look at the pyramid above. Every brick is the sum of the two bricks directly beneath it. If a brick is missing, use that rule — add to find a top brick, or subtract to find a bottom one.
- 1.Find a brick with both bricks below it known — add them for the top.
- 2.If the top is known but a bottom brick is missing, subtract the known bottom brick from the top.
- 3.Fill the pyramid until the missing brick appears.
✍️ Try it
The top brick is 9 and one bottom brick is 3. What is the other bottom brick? The two bottom bricks add to the top: 3 + ? = 9, so the missing brick is 6.
⚠️ Watch out
To go up you add; to go down you subtract. If the top is missing, add the two below; if a bottom brick is missing, subtract from the top.
See it in action
⚡ Time to play!
Build the pyramid from the bottom up. Each brick is the sum of the two below it.
2 + 3 = ?
Quick check
✅ VERIFICATION
In a number pyramid, the two bottom bricks are 4 and 5. What is the top brick?
⚡ Finish the activity above first to answer.
Keep going!