In front of you lie several number cards.
At the end of the row is the card with the target number.
If there is a plus in the row, look for two cards that together make exactly the target number.
If there is a minus, look for two cards with exactly that difference. The bigger card goes first.
The filled-in examples below show the answers.
Examples
Adding two cards
Finding the difference
For parents
What does this exercise practice?
The focused search for matching addends trains flexible number splitting and mental math. With minus, an eye for the gap between two numbers comes on top.
Common pitfalls
Children often try at random. Tip: for one card, think about which second card is still missing. With minus, the smaller card often ends up first -- the bigger one belongs there.
How to practice at home
Using playing cards, name a target number and look for two matching cards together, once for adding and once for taking away.
Related: Number Splitting, Card Math