Problem Solving Prompts

Learning Goals:

  • Estimate and record the mass of objects
  • Determine the missing numbers in equations
  • Investigate variables as unknown quantities

The Challenge:

A veterinarian is trying to measure the weight of three pets: a dog, a cat, and a rabbit. The only problem is that she can’t get them to sit still long enough to get a proper measurement!

In the chaos, she was able to record the following measurements:

Four coloured masses labelled below different combinations of pet silhouettes. Green rectangle labelled 10 kg below a rabbit and cat silhouette, orange rectangle labelled 20 kg below a dog and rabbit silhouette, red rectangle labelled 24 kg below a dog and cat silhouette, and a blue rectangle labelled with a question mark below a dog, cat, and rabbit silhouette.

Can she use this information to figure out the mass of all three pets combined?

Could she also use this information to figure out the mass of each individual pet?
Do you think she would need this information before solving the total mass of all three? Why or why not?

Questions and Prompts to Support your Child:

  • Which piece of information did you use first to eventually figure out the total mass? Why did you start there?
  • How do you know that those masses make sense for each type of pet?
  • Could knowing any of these masses help you estimate the approximate mass of any other animals? A raccoon? A bird?

Extensions & Adaptations:

  • If struggling with calculations, have a calculator handy!
  • If unable to get started, try looking for connections between the sets of pets, and brainstorming some combinations that might make sense as masses (i.e., since a rabbit and a cat weight 10 kg together, combinations might be 4 kg rabbit + 6 kg cat, 3 kg rabbit + 7 kg cat, 2 kg rabbit + 8 kg cat, etc.)
  • Check out Mashup Math or SolveMe Mobiles for some more algebraic puzzling!