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Welcome Number Ninjas
Chapter - Perimeter and Area
ज्ञान of the day
Topic - Ex 11.3 (part 1)
Let’s solve Homework..
Find the area of a circle inscribed in a square of side 20 cm.
Solution:
Radius of circle
=Half of Side of the square
= 20/2 = 10 cm
Area of the circle = πr2
= 3.1415 × 10 x 10= 314.15 cm2
Math LEGENDS
Sudhiksha, Bhargav, Sunidhi, Priya, Komal,
Heeba, Aditi raj, Sudiksha R.,
Tanmayee, Mansi, Alima, Samaira,
Riya,Mahima, Deepika, Dhairya, Bhavya,
Sindhuja, Pankti, Pihu
Math MARSHALS
Anaum,Aarushi, Vaishnavi mishra, ,
Anushka, Hithashree ,
satyam, Vinita, Vaishu,
Let’s go..
Ex - 11.3Part 1
Find the circumference of the circles with the following radius: (Take π = 22/7 )(a) 14 cm (b) 28 mm (c) 21 cm
Solution:-(a) Given, radius of circle = 14 cm
Circumference of the circle = 2πr= 2 × (22/7) × 14= 2 × 22 × 2 = 88 cm
(b) Given, radius of circle = 28 cmCircumference of the circle = 2πr= 2 × (22/7) × 28= 2 × 22 × 4 = 176 cm
(c) Given, radius of circle = 21 cmCircumference of the circle = 2πr= 2 × (22/7) × 21= 2 × 22 × 3 = 132 cm
Question 1:
Find the area of the following circles, given that:(a) radius = 14 mm (Take π = 22/7)
Question 2 :
Solution:Radius = 14 mm (Take π = 22/7)Given, radius of circle = 14 mmThen,Area of the circle = πr2
= 22/7 × 142= 22/7 × 196= 22 × 28= 616 mm2
Find the area of the following circles, given that:(b) diameter = 49 m
Question 2 :
Solution:Diameter = 49 mGiven, diameter of circle (d) = 49 mWe know that, radius (r) = d/2= 49/2= 24.5 mThen,Area of the circle = πr2
= 22/7 × (24.5)2= 22/7 × 600.25= 22 × 85.75= 1886.5 m2
Find the area of the following circles, given that:(c) radius = 5 cm
Question 2 :
Solution:Radius = 5 cmGiven, radius of circle = 5 cmThen,Area of the circle = πr2
= 22/7 × 52= 22/7 × 25= 550/7= 78.57 cm2
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If the circumference of a circular sheet is 154 m, find its radius. Also find the area of the sheet. (Take π = 22/7)
Question 3:
Solution:Circumference of the circle = 154 mThen, Circumference of the circle = 2πr154 = 2 × (22/7) × r154 = 44/7 × r
r = (154 × 7)/44r = (14 × 7)/4r = (7 × 7)/2r = 49/2r = 24.5 m
Now, Area of the circle = πr2
= 22/7 × (24.5)2
= 22/7 × 600.25= 1886.5 m2
So, the radius of circle is 24.5 and area of circle is 1886.5.
A gardener wants to fence a circular garden of diameter 21m. Find the length of the rope he needs to purchase, if he makes 2 rounds of fence. Also find the cost of therope, if it costs Rs 4 per meter. (Take π = 22/7)
Question 4:
Solution:
Question 5:
From a circular sheet of radius 4 cm, a circle of radius 3 cm is removed. Find the area of the remaining sheet. (Take π = 3.14)
Solution:
Saima wants to put a lace on the edge of a circular table cover of diameter 1.5 m. Find the length of the lace required and also find its cost if one meter of the lace costs ₹15. (Take π = 3.14).
Question 6:
Solution:
Find the perimeter of the adjoining figure, which is a semicircle including its diameter.
Question 7:
Solution:
Find the cost of polishing a circular table-top of diameter 1.6 m, ifthe rate of polishing is ₹15/m2. (Take π = 3.14)
Question 8:
Solution:
Diameter of the circular table-top = 1.6 m
Thus, radius (r) = d/2 = 1.6/2 = 0.8 m
Then, Area of the circular table-top = πr2
= 3.14 × 0.82
= 3.14 × 0.8 ×0.8
= 2.0096 m2
Cost for polishing 1 m2 area = ₹ 15
Cost for polishing 2.0096 m2 area
= ₹ 15 × 2.0096
= ₹ 30.144
Hence, the Cost for polishing 2.0096 m2
area is ₹ 30.144.
MENTI
NAME:
DATE:
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Per Class Price ₹ 2159 /- ₹ 5599 /- ₹7999/-
200 600 1200
₹ 2159 /- ₹ 5599 /- ₹ 7999 /-
Per Class Price ₹ 11 /- ₹ 9 /- ₹ 7 /-
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Homework Time!!
Find the area of a circle whose circumference is same as the perimeter of square of side 22 cm.
VEDANTUNUMBER NINJAS -Class 7
