Addition and subtraction

problem
Reverse trick

Age

7 to 11

Challenge level

Tell your friends that you have a strange calculator that turns numbers backwards. What secret number do you have to enter to make 141 414 turn around?
problem
Sisters and brothers

Age

7 to 11

Challenge level

Cassandra, David and Lachlan are brothers and sisters. They range in age between 1 year and 14 years. Can you figure out their exact ages from the clues?
problem
Clock face

Age

7 to 11

Challenge level

Where can you draw a line on a clock face so that the numbers on both sides have the same total?
problem
Gift stacks

Age

7 to 11

Challenge level

Use the information to work out how many gifts there are in each pile.
problem
A square of numbers

Age

7 to 11

Challenge level

Can you put the numbers 1 to 8 into the circles so that the four calculations are correct?
problem
The Deca Tree

Age

7 to 11

Challenge level

Find out what a Deca Tree is and then work out how many leaves there will be after the woodcutter has cut off a trunk, a branch, a twig and a leaf.
problem
A mixed-up clock

Age

7 to 11

Challenge level

There is a clock-face where the numbers have become all mixed up. Can you find out where all the numbers have got to from these ten statements?
problem
Number tracks

Age

7 to 11

Challenge level

Ben's class were cutting up number tracks. First they cut them into twos and added up the numbers on each piece. What patterns could they see?
problem
Polo square

Age

7 to 11

Challenge level

Arrange eight of the numbers between 1 and 9 in the Polo Square below so that each side adds to the same total.
problem
The money maze

Age

7 to 11

Challenge level

Go through the maze, collecting and losing your money as you go. Which route gives you the highest return? And the lowest?