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# https://vle.mathswatch.co.uk/images/questions/question812.png

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https://vle.mathswatch.co.uk/images/questions/question812.png

Nov 4, 2017

#2
+96189
+1

If we extended the top base of the figure by 8m and drew a perpendicular line to the base...the additional area would create a right "Pythagorean Triple" triangle with one of the legs  = 8m and a hypotenuse of 17m.....and the other leg = sqrt (17^2 - 8^2)  = sqrt (225) =  15m  = the length of the fence

Thus....disregarding the right triangle, we have a trapezoid with a height of 15m and two bases of 12m and 20m

So....the  area of a trapezoid  =

(height) / 2  *  (sum of the bases )   =

15 / 2  * ( 12 + 20)  =

7.5 *  32   =

240 m^2

So...we need three cans of weedkiller  =  3 * 19.75  =  59.25 pounds  (total cost)

Nov 4, 2017

#1
+537
-1

(AREA OF LAWN) 256 sqare meters

19.75*2 = 39.5

19.75/2 = 9.87500

9.87500 + 39.5 = 49.37500

(UNIT PRICE) 0.9875

0.9875 * 9 = 8.8875

9.87500 + 39.5 = 49.37500 + 8.8875 = 58.2625 ≈ 58.26

≈ \$58.26

Nov 4, 2017
edited by ProMagma  Nov 4, 2017
#2
+96189
+1

If we extended the top base of the figure by 8m and drew a perpendicular line to the base...the additional area would create a right "Pythagorean Triple" triangle with one of the legs  = 8m and a hypotenuse of 17m.....and the other leg = sqrt (17^2 - 8^2)  = sqrt (225) =  15m  = the length of the fence

Thus....disregarding the right triangle, we have a trapezoid with a height of 15m and two bases of 12m and 20m

So....the  area of a trapezoid  =

(height) / 2  *  (sum of the bases )   =

15 / 2  * ( 12 + 20)  =

7.5 *  32   =

240 m^2

So...we need three cans of weedkiller  =  3 * 19.75  =  59.25 pounds  (total cost)

CPhill Nov 4, 2017
#3
+537
-1

Dang.. I was close

ProMagma  Nov 4, 2017