9514 1404 393
Answer:
£59.25
Explanation:
The tricky part here is finding the height of the trapezoid shape of the lawn. You will notice the difference in lengths of the parallel edges is 20-12 = 8 meters. This means you can use the Pythagorean theorem to find the missing height, as it is the second leg of a right triangle with one leg 8 and hypotenuse 17.
h^2 = 17^2 -8^2 = 289 -64 = 225
h = √225 = 15
So, the lawn's shape is a trapezoid with bases 20 and 12 and height 15. These can go into the area formula ...
A = 1/2(b1 +b2)h
A = 1/2(20 +12)(15) = 240 . . . . . . square meters
__
That area is 2.4 times 100 square meters. That means 2.4 cans of weedkiller are all that are needed. If we can only purchase whole cans, then we need to purchase 3 cans of weedkiller, for a cost of ...
£19.75 × 3 = £59.25
The cost of the cans of weedkiller needed will be £59.25.