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## 'Top-heavy Pyramids' printed from http://nrich.maths.org/

These are top-heavy pyramids. The blue one has $21$ at the apex
(top) and the red one has $31$.

A pair of numbers are added to make the number
above that pair.

In the blue top-heavy pyramid whose base is $4$,
$5$ and $7$, $4 + 5 = 9$, so $9$ is placed between and above the
$4$ and the $5$.

$5 + 7 = 12$ and $9 + 12 = 21$.

Use the numbers in the box below to make the base
of a top-heavy pyramid whose top number is $200$.