Why do this problem?
challenges children's understanding of the concept of area rather than simply requiring them to follow a rule for finding areas of rectangles. These calculations should also help learners to see the advantages of the metric system as well as understand it more fully!
As an introduction to this problem, invite children to tell you about different words they have heard used in the context of measuring distance. (This might reveal some interesting misconceptions.) Focus on those that are units of measurement and ask the learners to suggest when each might be used. You could group the words on the board to show those that are metric units and those that are
imperial, which would lead into a discussion of which are most common nowadays.
Go onto look at the problem itself, perhaps by telling the story orally and drawing Grandpa's sketch yourself on the board. Ask children to talk in pairs about how they would check the calculation, and then discuss it as a whole class. You might find that some pairs would like to annotate your drawing which would be helpful! Set the children off on the other parts of the question in pairs or
small groups, making sure there is paper available should they want it.
In a plenary, take the opportunity to share different ways of working on the solutions which show good understanding of the concept of area and the use of square units. Which system of units do the children think is easiest to work with?
Have you drawn a diagram or sketch?
Can you find any complete square yards or complete square feet?
Children may enjoy measuring some objects in the classroom and using both metric and imperial measures to work out their areas.
Drawing a diagram of the two sketches on squared paper might help when it comes to dividing them up into complete square yards and square feet.