In the figure, PQST is a parallelogram and TSR is a straight line. If the area of \(\bigtriangleup\)QRS is 20cm2, find the area of the trapezium PQRT.
35cm2
65cm2
70cm2
140cm2
Explanation
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Discussions (13)
First, the rae of the triangle was given, bring the triangle out and solve for the height
Area= 1/2 bh
20 = 1/2 × 8 × h
20= 4h
h = 5
Since height is gotten,
To get area of the parallelogram
Area= 1/2 (a +b )h
Area= 1/2 (10+ 18) 5
Area= 1/2 × 28 × 5
Area = 14 × 5 = 70cm²
Using ½bh as the area of a triangle only works for right angled triangles, don't forget we have 3 formulas for getting the area of a triangle:
1. ½bh - for right angled triangles
2. ½absin∅ - when you are given two sides of the triangle and the angle between the two sides given
3. heron's formula:
√[S(S - a)(S - b)(S - c)] - where: S = (a + b + c)/2 used when you are given the 3 sides of the triangle.
From the question, they never mentioned it that the triangle is right angled, neither did they give us the angle between any of the two sides, so why are you guys using ½bh to calculate the area of the triangle?, pls explain.
