Math Background

Comparing Lengths, Weights, and Capacities: When Students Ask

  • How can the same object have different measurements?
    Use your hand to measure the length of a desk or table. Ask a volunteer to record the measurement. Then ask a child to do the same and record the result. Talk about why the results are different, pointing out that the hands are different sizes. Discuss the concept that the size of the measuring unit will affect the measurement. Explain that long ago, people used to measure in similar ways; even today, the height of horses is measured in hands.
  • Why aren't the biggest things always the heaviest?
    Provide an assortment of classroom objects. Include some large objects that are light, such as an inflated balloon and a large plastic container. Ask a volunteer to choose two objects, and ask which is bigger and which is smaller. Record the answers. Then ask the child to hold each object and decide which is heavier. Verbally emphasize the results: The box is bigger. It is lighter. Point out instances when the bigger object is lighter. Help children understand that size and weight are two different measurements.
  • What can I do to estimate how much a container can hold?
    Remind children that an estimate is a reasonable guess. Display a container, a bowl of rice, and a cup. Ask children to estimate how many cups of rice the container will hold. Record the different estimates. Then have children keep a tally as a volunteer fills the container with cups of rice. Ask how many cups the container holds, and discuss the estimates. Ask how many cups a container twice the size or half the size would hold. Continue with other containers.

Houghton Mifflin Math Grade K