Now your child has practiced subtraction in columns without exchange, they are ready to understand why we can exchange a group of tens to add more to the units column.
Explain that when the units digit is not large enough to take away from, they will need to borrow a ten from the tens column to make the units number larger. They must remember to cross out the tens digit they are borrowing from and write the new tens digit in its place.
Watch the clip below to practice with your child.