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BTN: Calculating area using locust plagues

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Man's legs stand on lawn covered with locusts
BTN: Calculating area using locust plagues

SUBJECTS:  Maths

YEARS:  7–8


How many locusts in a plague?

Find out just how big the threat of locusts can be and how farmers try to prevent the plagues from getting out of control.

This clip provides context for a combination of area, area units and rate problems.


Things to think about

  1. 1.What do you think the average farm size is in your state? Do a quick internet search to check your estimate. The area is measured in hectares. A hectare is a square area 100 m x 100 m. How many square metres is that?
  2. 2.In the right conditions locusts can lay up to 10,000 eggs per square metre. A tennis court is used as the example of an area that could contain up to 2,608,000 eggs. How would they arrive at this number mathematically? Hint: A tennis court is 23.77 m long by 10.97 m wide. Estimate the area 24 x 11 = 264 square metres. So approximately 264 x 10,000 = 2,640,000 eggs in an area the size of a tennis court. Now recalculate using the exact lengths. Is your answer close to the figure suggested in the clip?
  3. 3.If a farm is 2 km x 3 km, the area is 2,000 m x 3,000 m = 6,000,000 square metres. Consider two farms: Farm A, 1.5 km x 2 km with an average of 800 locust eggs per square metre; and Farm B, 0.8 km x 3 km with an average of 700 locust eggs per square metre. Which farm, A or B, has the largest number of locust eggs? The correct number of eggs on Farm A and Farm B is included in the following: 24,000,000; 2,400,000,000; 1680,000,000; 1,680,000.
  4. 4.Locusts can rapidly devour crops. A farmer on a 3000 ha property has a wheat crop which he estimates would yield six tonnes of grain per hectare. A locust swarm wipes out 25% of his crops. How many tonnes of grain has he lost in production? The answer is included in the following: 450, 4500, 1350, 13500.



Date of broadcast: 14 Sep 2010


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