- Mensuration
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- Perimeter
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- Area
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- Perimeter and Area of Different Figure
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- How to solve the Area and Perimeter problems
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- Solved Examples

Given below are the

a) Concepts questions

b) Calculation problems

c) Multiple choice questions

d) Long answer questions

e) Fill in the blank's

1. Calculate the area in each case

- Triangle have sides as a=5 cm ,b=4 cm,c=3 cm
- Equilateral triangle having side a=2 cm
- Right angle triangle have base=4 cm and Height =3 cm
- Square whose diagonal is 10 cm
- Rectangle whose length and breath are 6 and 4 cm
- Parallelogram whose two sides are 10 cm and 16 cm and diagonal is 14 cm
- Parallelogram whose base is 10 cm and height is 14 cm
- Rhombus of diagonals to 10 and 24 cm
- Two sides of trapezium are 36 and 24 cm and its altitude is 12 cm.

a) $s=\frac{a+b+c}{2}$ =6

Area

$A=\sqrt{s(s-a)(s-b)(s-c)}$=6cm

b) Area of equilateral

$A=\frac{\sqrt{3}}{4}a^{2}=\sqrt{3}$

c) Area of triangle

A=(1/2)BH=6cm

d) Area of square in terms diagonal

A=(1/2)d

e) Rectangle area is given by

A=LXB=24cm

f) In parallelogram whose two sides and diagonal are given, Area is given by

$A=\sqrt{s(s-a)(s-b)(s-d)}$

Where $s=\frac{a+b+d}{2}$

So s=20cm

So A=80(3)

g) Area is given by

A=Base X height =10X14=140cm

h) Area is given by

A=(1/2)d

i) Area of trapezium is given by

A=(1/2)(Sum of parallel sides) Altitude

A=360cm

2)

a) Heron formula for area of triangle is not valid of all triangles

b) If each side of the triangles is tripled, the area will becomes 9 times

c) Base and corresponding altitude of the parallelogram are 8 and 5 cm respectively.Area of parallelogram is 40 cm

d) If each side of triangle is doubled, the perimeter will become 4 times

e) If p is the perimeter of the triangle of sides a,b,c ,the area of triangle is

$A=\frac{1}{4}\sqrt{p(p-2a)(p-2b)(p-2c)}$

f) When two triangles are congruent, there areas are same

g) Heron’s belongs to America

h) If the side of the equilateral triangle is a rational number, the area would always be irrational number

- False
- True
- True
- False
- True
- True
- False
- True

3) The difference between sides at right angles in a right angled triangle is 14 cm. The area of the triangle is 120 cm

a) 80

b) 45

c) 60

d) 64

Let y be one of the at right angle ,then another side will be y-14

Now we know that

A=(1/2)BH

120=(1/2)y(y-14)

y

(y-24)(y+10)=0

y=24

So other side is 10

From pythogrous theorem

$hyp=\sqrt{10^{2}+24^{2}}$=26cm

So perimeter will be =10+24+26=60 cm

4. Find the area of the equilateral triangle whose perimeter is 180 cm?

Which of the following is true?

a)900(3)

b)300(3)

c)200(3)

d) None of these

P=3a => a=P/3=60 cm

Area of equilateral

$A=\frac{\sqrt{3}}{4}a^{2}$

5) One diagonal and side of the rhombus are 24 and 13 cm respectively, Find the Area and other diagonal size?

a) 160 cm

b) 120 cm

c) 120 cm

d) None of the above

6) ABCD is a trapezium with AB =10cm, AD=5 cm, BC=4 cm and DC =7 cm?

Find the area of the ABCD

a) 34 cm

b) 28cm

c) 20 cm

d) None of these

BC is the altitude between the two parallel sides AB and DC

So Area of trapezium will be given by

$A=\frac{1}{2}BC(AB+DC)$=34cm

7) Find the area and perimeter of the right angle triangle whose hypotenuse is 5 cm and Base is 4 cm

a) 6 cm

b) 12 cm

c) 4 cm

d) 12 cm

By pythogorous theorem

$height=\sqrt{hyp^{2}-base^{2}}=\sqrt{25-19}=3$

So Area =(1/2) XBase X height=6 cm

Perimeter = 5+4+3=12 cm

8) In an isosceles triangle ?ABC with AB = AC=13 cm. D is mid point on BC. Also BC=10 cm

Which of the following is true?

a) Area of Triangle ABD and ADC are equal

b) Area of triangle ABD is 30 cm

c) Area of triangle ABC is 60 cm

d) All the above

ABD an ADC are congruent triangle, So Area of Triangle ABD and ADC are equal

Also From pythogorous theorem, AD will be given as

$AD=\sqrt{AB^{2}-BD^{2}}=\sqrt{169-25}=12cm$

So Area of triangle ABC=(1/2)X base X height=60 cm

a) 12 cm

b) 14 cm

c) 10cm

d) 13 cm

For triangle, all the sides are given, calculating the area using Heron formula

A=336 cm

Now for parallelogram, Area is given by

A= Base X Altitude

336=28 X H

Or H=12 cm

10) Find the percentage increase in size of the triangle if each side is doubled

a)

b) 300%

c) 400%

d) None of the above

Perimeter of rectangle of length 24 cm and diagonal 26 cm |
22cm |

Perimeter of the square of side 10 cm |
17 cm |

Triangle of sides 4,5,6 cm respectively |
40 cm |

Perimeter of parallelogram of two sides 5 and 6 cm respectively |
68 cm |

Given below are the links of some of the reference books for class 9 Math.

- Mathematics for Class 9 by R D Sharma One of the best book for studying class 9 level mathematics. It has lot of problems to be solved.
- Secondary School Mathematics for Class 9 by R S Aggarwal This is also as good as R.D. Sharma. Either this or the book by R.D. Sharma will do. I find book R.S. Aggarwal little bit more challenging than the one by R.D. Sharma.
- Pearson IIT Foundation Series - Maths - Class 9 Buy this book if you want to challenge yourself further and want to prepare for JEE foundation.
- Pearson IIT Foundation Physics, Chemistry & Maths combo for Class 9 Only buy if you are prepared to study extra topics and want to take your studies a step further. You might need help to understand topics in these books.

You can use above books for extra knowledge and practicing different questions.

Class 9 Maths Class 9 Science

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