Number (estimation): Robin & Mole
The Problem
On a cold winter’s day, Robbie the adult robin was desperately searching for food in his territory. Although the ground was frozen solid, a family of moles had created a number of molehills (soft piles of soil), which Robbie knew might contain fat, juicy worms.
Useful facts
- Adult robins must eat at least ten earthworms a day in the winter.
- You would expect to find 1 or 2 earthworms in a child-sized bucketful of soil.
Use these useful facts to answer the following questions:
- What is the smallest number of molehills that Robbie would need to visit on a single winter’s day?
- What is the largest number of molehills that Robbie would need to visit on a single winter’s day?
Despite their cute appearance, robins are aggressively territorial. This means that they consider an area of land their own and and aren’t keen to share it with anyone, especially other robins!
Visualising the Problem and Getting Started
Rui said, “To find out the smallest number and largest number of molehills that Robbie needs to visit on a single winter’s day, you first need to know how many ‘bucketfuls’ of soil there are in a molehill.”
Do you agree with Rui?
Look closely at the picture below. It shows the relative sizes of an adult robin and an average-sized molehill.
Approximately, how many bucketfuls of soil do you think there are in a molehill?
