What two numbers add up to 40?

Drag and drop the number from the right to the number on the left so they both add up to 40.

In other words: Click and hold the button down while moving the number. Release the button when over the other number.

Number Bonds To 10  |  Number Bonds To 20  |  Number Bonds To 30  | 
Number Bonds To 40  |  Number Bonds To 50  |  Number Bonds To 100