Multiples Maths Problems

1. Here is a 100 grid with some numbers shaded:

What do all the numbers shaded blue have in common?

What do you notice about all the numbers shaded pink?

Can you work out why two of the numbers are shaded in a maroon colour?

Below are parts of a 100 square. Each one has a different set of rules for how it has been shaded. Can you work out the rules for each?

2.

3.

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5.

http://nrich.maths.org/5429

Have a go at one question, a couple of questions or all of them!