This clip shows how to subtract 10 from a two-digit number. The clip is illustrated by 68 ants departing on leaf boats in tens. The ants are sent off in teams of 10 to participate in an ant regatta. As the boats depart, we see 10 being taken away from 68, and then from 58, etcetera on a notepad. Eventually there are only 8 ants remaining who get into the last boat.
Pause the clip at the end when the clipboard shows all of the subtractions. Ask the class if they can see a pattern. Point out that the tens column goes down each time but the unit column stays the same. Explain that this is because we are deducting 10 and zero units each time so the tens column is the one that changes. Give the children some more practice with another two-digit number. Display a 100 number square and use this as a visual aid.