A door of length 2.5m and breadth 1.5m is fitted in a wall the length and breadth of the wall are 6m and 4.5m respectively. Find the cost of white washing the wall at the rate of ₹30 per square. M
Answers
area of door=length×breadth
area of wall=length of wall×breadth of wall
area to be white washed=area of wall-area of door
cost of white washing = area left ×cost
Chapter List
Chapter 1 to 4
Chapter 5 to 8
Chapter 9 to 12
Chapter 13 to 15
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Class 7 Maths
Perimeter And Area
Square and Rectangle
Perimeter of square = 4
×
Side
Area of square = Side
×
Side = (Side)2
Perimeter of Rectangle = 2
×
(Length + Breadth)
Area of Rectangle = Length
×
Breadth
Exercise 11.1
Question 1: The length and the breadth of a rectangular piece of land are 500m and 300 m respectively. Find (i) Its areas (ii) the cost of the land, if 1m2 of the land costs Rs 10,000.
rectangle
Answer: Given: Length = 500 m and breadth = 300 m, cost of 1m2 of land = Rs. 10,000
Area = Length
×
Breadth
=
500
×
300
=
150000
sq m
Price of Land = Area
×
cost per sq m
=
150000
×
10000
= Rs. 1,500,000,000
Question 2: Find the area of a square park whose perimeter is 320 m.
Answer: Given, Perimeter of a square park = 320 m
Side = Perimeter ÷ 4
=
320
÷
4
=
80
m
Area of Square = Side2
=
80
2
=
6400
sq m
Question 3: Find the breadth of a rectangular plot of land, if its area is 440 m2 and the length is 22m. Also find its perimeter.
rectangle
Answer: Given: Length = 22m and area of the field = 440 m2
Area = Length
×
Breadth
So, Breadth = Area ÷ Length
=
440
÷
22
=
20
m
Now, perimeter = 2(length + breadth)
=
2
(
22
+
20
)
=
2
×
42
=
84
m
Question 4: The perimeter of a rectangular sheet is 100 cm. If the length is 35 cm, find its breadth. Also find the area.
rectangle
Answer: Given perimeter = 100 cm and length = 35 cm
Perimeter = 2(Length + Breadth)
Or,
100
=
2
(
35
+
breadth
)
Or,
35
+
breadth
=
50
Or, breadth
=
50
–
35
=
15
c
m
Area = length
×
breadth
=
35
×
15
=
525
sq cm
Question 5: The area of a square park is the same as of a rectangular park. If the side of the square park is 60m and the length of the rectangular park is 90m, find the breadth of the rectangular park.
rectangle
Answer: Given; side of square park = 60 m and length of rectangular park = 90 m
Area of square park = Side2
=
60
2
=
3600
sq m
Area of rectangular park = Area of rectangular park
Hence,
3600
=
90
×
breadth
Or, breadth
=
3600
÷
90
=
40
m
Question 6: A wire is in the shape of a rectangle. Its length is 40cm and breadth is 22cm. If the same wire is rebent in the shape of a square, what will be the measure of each side? Also find which shape encloses more area?
Answer: Given; length = 40 cm and breadth = 22 m
Perimeter = 2(length + breadth)
=
2
(
40
+
22
)
=
2
×
62
=
124
cm
Perimeter of rectangle = Perimeter of square
Or,
124
=
4
×
Side
Or, Side
=
124
÷
4
=
31
c
m
Now, area of square = Side2
=
31
2
=
961
sq cm
Area of rectangle = Length
×
Breadth
=
40
×
22
=
880
sq cm
Hence, area of square > area of rectangle
Question 7: The perimeter of a rectangle is 130 cm. If the breadth of the rectangle is 30 cm, find its length. Also find the area of the rectangle.
Answer: Given; perimeter = 130 cm and breadth = 30 cm
Perimeter = 2(length + breadth)
Or,
130
=
2
(
length
+
30
)
Or,
length
+
30
=
65
Or, length
=
65
–
30
=
35
c
m
Area of rectangle = Length
×
Breadth
=
35
×
30
=
1050
sq cm