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Mathematics

Use the information given in the given figure to find:

(i) the length of AC.

(ii) the area of △ ABC.

(iii) the length of BD, correct to one decimal place.

Use the information given in the given figure to find: Area of a Trapezium and a Polygon, Concise Mathematics Solutions ICSE Class 8.

Area Trapezium Polygon

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Answer

(i) Given:

In triangle ABC,

Base of the triangle = 24 cm

Height of the triangle = 7 cm

Let h be the hypotenuse of the triangle.

In a right-angled triangle, using the Pythagorean theorem,

Base2 + Height2 = Hypotenuse2

⇒ (24)2 + (7)2 = h2

⇒ 576 + 49 = h2

⇒ h2 = 625

⇒ h = 625\sqrt{625}

⇒ h = 25 cm

Hence, the length of AC = 25 cm.

(ii) As we know, the area of a triangle = 12\dfrac{1}{2} x side x height

= 12\dfrac{1}{2} x 24 x 7 cm2

= 12\dfrac{1}{2} x 168 cm2

= 84 cm2

Hence, the area of the triangle = 84 cm2.

(iii) The base of the triangle = 25 cm

Let the height of the triangle be h.

As we know, the area of a triangle = 12\dfrac{1}{2} x side x height

[∵ Both areas remain same since they represent the area of the same triangle.]

12\dfrac{1}{2} x 25 x h = 84

⇒ 25 x h = 2 x 84

⇒ 25 x h = 168

⇒ h = 16825\dfrac{168}{25}

⇒ h = 6.7 cm

Hence, the length of BD = 6.7 cm.

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