ABCD is a trapezium with AB||CD. If AB = 11 cm, CD = 25 cm, AD = 15 cm and BC = 13 cm, find the area of trapezium ABCD.
Answers
Step-by-step explanation:
Here we will learn how to use the formula to find the area of trapezium.
Area of trapezium ABCD = Area of ∆ ABD + Area of ∆ CBD
= 1/2 × a × h + 1/2 × b × h
= 1/2 × h × (a + b)
= 1/2 (sum of parallel sides) × (perpendicular distance between them)
Area of trapezium
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Worked-out examples on area of trapezium
1. The length of the parallel sides of a trapezium are in the rat: 3 : 2 and the distance between them is 10 cm. If the area of trapezium is 325 cm², find the length of the parallel sides.
Solution:
Let the common ration be x,
Then the two parallel sides are 3x, 2x
Distance between them = 10 cm
Area of trapezium = 325 cm²
Area of trapezium = 1/2 (p₁ + p₂) h
325 = 1/2 (3x + 2x) 10
⇒ 325 = 5x × 5
⇒ 325 = 25x
⇒ x = 325/25
Therefore, 3x = 3 × 13 = 39 and 2x = 2 × 13 = 26
Therefore, the length of parallel sides area are 26 cm and 39 cm.
2. ABCD is a trapezium in which AB ∥ CD, AD ⊥ DC, AB = 20 cm, BC = 13 cm and DC = 25 cm. Find the area of the trapezium.
find the area of trapezium
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Solution:
From B draw BP perpendicular DC
Therefore, AB = DP = 20 cm
So, PC = DC - DP
= (25 - 20) cm
= 5 cm
Now, area of trapezium ABCD = Area of rectangle ABPD + Area of △ BPC
△BPC is right angled at ∠BPC
Therefore, using Pythagoras theorem,
BC² = BP² + PC²
13² = BP² + 5²
⇒ 169 = BP² + 25
⇒ 169 - 25 = BP²
⇒ 144 = BP²
⇒ BP = 12
Now, area of trapezium ABCD = Area of rectangle ABPD + Area of ∆BPC
= AB × BP + 1/2 × PC × BP
= 20 × 12 + 1/2 × 5 × 12
= 240 + 30
= 270 cm²
3. Find the area of a trapezium whose parallel sides are AB = 12 cm, CD = 36 cm and the non-parallel sides are BC = 15 cm and AG = 15 cm.
Let one side of trapezium is x, then other side parallel to it = 2x
Area of trapezium = 165 cm²
Height of trapezium = 10 cm
Now, area of trapezium = 1/2 (p₁ + p₂) × h
⇒ 165 = 1/2(x₁ + 2x) × 10
⇒ 165 = 3x × 5
⇒ 165 = 15x
⇒ x = 165/15
⇒ x = 11
Therefore, 2x = 2 × 11 = 22
Therefore, the two parallel sides are of length 11 cm and 22 cm.
These are the above examples explained step by step to calculate the area of trapezium