Problems

Salome made 20 cupcakes to take to a party.
She didn’t want all of her cupcakes to look the same.

She lined them up and put green icing on every second cupcake.
Then she put a red cherry on every third cupcake.
Then she put a brown chocolate square on every fourth cupcake.
She didn’t put anything on the first cupcake.

How many cupcakes had no decoration?
Did any cupcakes get all three decorations?

Hint:

To get started you may want to draw 20 circles to represent the cupcakes and use colours or letters to represent the decorations.

(Adapted from nrichmaths.org)