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Mathematics

In the given figure, if area of triangle ADE is 60 cm2; state, giving reason, the area of :

(i) parallelogram ABED;

(ii) rectangle ABCF;

(iii) triangle ABE.

In the given figure, if area of triangle ADE is 60 cm2; state, giving reason, the area of : Area Theorems, Concise Mathematics Solutions ICSE Class 9.

Theorems on Area

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Answer

In the given figure, if area of triangle ADE is 60 cm2; state, giving reason, the area of : Area Theorems, Concise Mathematics Solutions ICSE Class 9.

(i) We know that,

Area of triangle is half that of a parallelogram, on the same base and between the same parallels.

From figure,

△ ADE and parallelogram ABED lies on same base DE and between same parallel lines AB and DE.

∴ Area of △ ADE = 12\dfrac{1}{2} Area of parallelogram ABED

⇒ Area of parallelogram ABED = 2 × Area of △ ADE

⇒ Area of parallelogram ABED = 2 × 60 = 120 cm2.

Hence, area of parallelogram ABED = 120 cm2.

(ii) We know that,

Area of parallelogram is equal to area of a rectangle on the same base and between same parallel lines.

From figure,

Parallelogram ABED and rectangle ABCF lie on lie on same base AB and between same parallel lines AB and CD.

∴ Area of rectangle ABCF = Area of parallelogram ABED = 120 cm2.

Hence, area of rectangle ABCF = 120 cm2.

(iii) We know that,

Area of a triangle is half that of a parallelogram on the same base and between the same parallels.

∴ Area of triangle ABE = 12\dfrac{1}{2} Area of parallelogram ABED

= 12×120\dfrac{1}{2} \times 120 = 60 cm2.

Hence, area of triangle ABE = 60 cm2.

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