#### Chapter 12 Heron's Formula R.D. Sharma Solutions for Class 9th MCQ's

**Multiple Choice Questions**

Mark the correct alternative in each of the following:

1. The sides of a triangle are 16 cm, 30 cm, 34 cm. Its area is:

(a) 225 cm

^{2}
(b) 225âˆš3 cm

^{2}
(c) 225âˆš3 cm

^{2}
(d) 450 cm

^{2}**Solution**

2. The base of an isosceles right triangle is 30 cm. Its area is

(a) 225 cm

(a) 225 cm

^{2}
(b) 225âˆš3 cm

^{2}
(c) 225âˆš3 cm

^{2}
(d) 450 cm

^{2}**Solution**

Let ABC be the right triangle in which âˆ B = 90Â°

Now,

base = BC

perpendicular = AB

hypotenuse = AC

BC = 30 cm (given)

â–³ABC is an isosceles right angled triangle. We know that hypotenuse is the longest side of the right triangle.

So, AB = BC = 30 cm

Area of â–³ABC = 1/2Ã— base Ã— height

= 1/2Ã— BC Ã— AB

= 1/2Ã— 30 Ã— 30

= 450 cm

^{2}3. The sides of a triangle are 7 cm, 9 cm and 14 cm. Its area is

(a) 12âˆš5 cm

^{2}

(b) 12âˆš3 cm

^{2}
(c) 24âˆš5 cm

^{2}
(d) 63 cm

^{2}**Solution**

4. The sides of a triangular field are 325 m, 300 m and 125 m. Its area is

(a) 18750 m

^{2}
(b) 37500 m

^{2}
(c) 97500 m

^{2}
(d) 48750 m

^{2}

^{}Solution5. The sides of a triangle are 50 cm, 78 cm and 112 cm. The smallest altitude is

(a) 20 cm

(b) 30 cm

(c) 40 cm

(d) 50 cm

**Solution**

6. The sides of a triangle are 11 m, 60 m and 61 m. The altitude to the smallest side is

(a) 11 m

(b) 66 m

(c) 50 m

(d) 60 m

**Solution**

7. The sides of a triangle are 11 cm, 15 cm and 16 cm. The altitude to the largest side is

(a) 30âˆš7 cm

(b) 15âˆš7/2 cm

(c) 15âˆš7/4 cm

(d) 30 cm

**Solution**

^{2}, what is the perimeter of the triangle?

(a) 8+âˆš2 cm

^{2}

(b) 8 + 4âˆš2 cm

^{2}

(c) 4 + 8âˆš2 cm

^{2}
(d) 12âˆš2 cm

^{2}**Solution**

We are given the area of an isosceles right triangle and we have to find its perimeter.

Two sides of isosceles right triangle are equal and we assume the equal sides to be the base and height of the triangle. We are asked to find the perimeter of the triangle

Let us take the base and height of the triangle be x cm.

Area of a isosceles right triangle (A) having base x cm and height x cm is given by:

9. The lengths of the sides of Î”ABC are consecutive integers. It Î”ABC has the same perimeter as an equilateral triangle with a side of length 9 cm, what is the length of the shortest side of Î”ABC?

(a) 4

(b) 6

(c) 8

(d) 10

**Solution**

We are given that triangle ABC has equal perimeter as to the perimeter of an equilateral triangle having side 9 cm. The sides of triangle ABC are consecutive integers. We are asked to find the smallest side of the triangle ABC .

Perimeter of an equilateral triangle, say P having side 9 cm is given by

10. In figure 12.35, the ratio AD to DC is 3 to 2. If the area of Î” ABC is 40 cm2, what is the area of Î” BDC ?

**Solution**

11. The base and hypotenuse of right triangular are respectively 5 cm and 13 cm long. Its area is:

(a)25 cm

(b) 28 cm

^{2}(b) 28 cm

^{2}
(c) 30 cm

^{2}
(d) 40 cm

^{2}**Solution**

12. The length of a median of an equilateral triangle is x cm, then its area is:

(a) x

^{2}
(b) âˆš3/2 x

^{2}
(c) x

^{2}/âˆš3
(d) x

^{2}/2**Solution**

We are given the length of median of an equilateral triangle by which we can calculate its side. We are asked to find area of triangle in terms of x

Altitude of an equilateral triangle say L, having equal sides of a cm is given by, where, L = x cm

13. The length of each side of an equilateral triangle of area 4âˆš3 cm

^{2}is
(a) 4 cm

(b) 4/âˆš3 cm

(c) âˆš3/4 cm

(d) 3 cm

**Solution**

14. If every side of a triangle is doubled, then increase in the area of the triangle is

(a) 100âˆš2 %

(b) 200 %

(c) 300 %

(d) 400 %

**Solution**

15. A square and an equilateral triangle have equal perimeters. If the diagonal of the square is 12âˆš2 cm, then area of the triangle is

(a) 24âˆš2 cm

^{2}
(b) 24âˆš3 cm

^{2}
(c) 48âˆš3 cm

^{2}
(b) 64âˆš3 cm

^{2}**Solution**