A group arrives at an airport to check in their 21 bags. They each want to keep a piece of hand luggage. Unable to work out how many bags they will need to check in, they call out for El Nombre who materialises and explains how to solve the problem. There are 6 in the group and each of them wants to take a bag as hand luggage, so they need to count back 6 from 21. They count back in ones and all agree that the answer is 15.
Continue with the idea from the clip. If possible, use bags within the classroom so the children have a concrete image to begin with until they are secure. Ask the class "if we are taking 21 bags on holiday but 5 are being taken onto the plane with Juan's family, then how many will we have to check in?" Count backwards until the answer is found. Record on the board so the children can see the subtraction written out. Continue with a few more examples. Give the children some independent practice using multilink cubes if they need concrete support.