Addition and subtraction

problem

Dodecamagic

Age

7 to 11

Challenge level

2 out of 3

Here you see the front and back views of a dodecahedron. Each vertex has been numbered so that the numbers around each pentagonal face add up to 65. Can you find all the missing numbers?
problem

Prison Cells

Age

7 to 11

Challenge level

2 out of 3

There are 78 prisoners in a square cell block of twelve cells. The clever prison warder arranged them so there were 25 along each wall of the prison block. How did he do it?
problem

How Many Eggs?

Age

7 to 11

Challenge level

2 out of 3

Peter, Melanie, Amil and Jack received a total of 38 chocolate eggs. Use the information to work out how many eggs each person had.
problem

Special 24

Age

7 to 11

Challenge level

2 out of 3

Find another number that is one short of a square number and when you double it and add 1, the result is also a square number.
problem

Zargon Glasses

Age

7 to 11

Challenge level

2 out of 3

Zumf makes spectacles for the residents of the planet Zargon, who have either 3 eyes or 4 eyes. How many lenses will Zumf need to make all the different orders for 9 families?
problem

Magic Circles

Age

7 to 11

Challenge level

2 out of 3

Put the numbers 1, 2, 3, 4, 5, 6 into the squares so that the numbers on each circle add up to the same amount. Can you find the rule for giving another set of six numbers?
problem

Arranging the Tables

Age

7 to 11

Challenge level

2 out of 3

There are 44 people coming to a dinner party. There are 15 square tables that seat 4 people. Find a way to seat the 44 people using all 15 tables, with no empty places.
problem

Number Juggle

Age

7 to 11

Challenge level

2 out of 3

Fill in the missing numbers so that adding each pair of corner numbers gives you the number between them (in the box).
problem

A Rod and a Pole

Age

7 to 11

Challenge level

2 out of 3

A lady has a steel rod and a wooden pole and she knows the length of each. How can she measure out an 8 unit piece of pole?
problem

Add 3 Dice

Age

7 to 11

Challenge level

2 out of 3

Three dice are placed in a row. Find a way to turn each one so that the three numbers on top of the dice total the same as the three numbers on the front of the dice. Can you find all the ways to do this?