You may also like

problem icon

Speedy Sidney

Two trains set off at the same time from each end of a single straight railway line. A very fast bee starts off in front of the first train and flies continuously back and forth between the two trains. How far does Sidney fly before he is squashed between the two trains?

problem icon


Water freezes at 0°Celsius (32°Fahrenheit) and boils at 100°C (212°Fahrenheit). Is there a temperature at which Celsius and Fahrenheit readings are the same?

problem icon

Air Nets

Can you visualise whether these nets fold up into 3D shapes? Watch the videos each time to see if you were correct.

Food Chains

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Here is a food chain:

Foodchain - cat, bird, caterpillar images Wikipedia (Creative Commons); Mullein image (c)


A wildcat will eat 3 birds every day. These three birds will eat 10 caterpillars each, every day, totaling 30 caterpillars. The 30 caterpillars will eat one small bush together every day.
a. The area that these animals live in currently has 500 small bushes: calculate the number of the other animals.
b. As you go up the food chain, the amount of energy available to the following predator decreases. For this food chain, the amount of energy available decreases by 25% for every level in the chain. Calculate how much more energy the wildcat could obtain from becoming a vegetarian and eating the bush rather than from eating birds.
c. One year, a bacteria kills 5000 caterpillars. What effect will this have on the food chain?
d. What would happen to the cat, bird and caterpillar populations if the cats decided to become vegetarians and eat bushes to keep alive instead of starving?