The DAV Maths Book Class 4 Solutions and DAV Class 4 Maths Chapter 12 Brain Teasers Solutions of Area offer comprehensive answers to textbook questions.
DAV Class 4 Maths Ch 12 Brain Teasers Solutions
Question 1.
Tick (✓) the correct answer.
(a) The area of the shaded portion is
(i) 72 sq. cm
(ii) 30 sq. cm
(iii) 102 sq.cm
(iv) 42 sq .cm
Answer:
Area of shaded portion = Area of outer rectangle – Area of inner rectangle
Area of outer rectangle = 9 cm × 8 cm = 72 sq. cm
Area of inner rectangle = 5 cm × 6 cm = 30 sq. cm
Area of shaded portion = 72 cm2 – 30 cm2
= 42 sq. cm
Hence, option (iv) is correct.
(b) Length of a rectangle is 12 cm and its breadth is 4 cm less than the length. The area of the rectangle is –
(i) 40 sq. cm
(ii) 96 sq. cm
(iii) 40 cm
(iv) 96 cm
Answer:
Length of rectangle = 12 cm
Breadth of rectangle = L – 4 cm
= 12 – 4
= 8 cm
so, Area of rectangle = 12 cm × 8 cm
= 96 sq. cm
Hence, option (ii) is correct.
(c) The best unit to measure area is:
(i) rectangle
(ii) square
(iii) triangle
(iv) circle
Answer:
(ii) square
(d) Area of the given figure is squares.
(i) 6
(ii) 10
(iii) 12
(iv) 5
Answer:
(i) 6
Hence option (i) is correct.
(e) Area of a rectangle of length 7 cm and breadth 4 cm is
(i) 28 cm
(ii) 22 sq. cm
(iii) 22 cm
(iv) 28 sq. cm
Answer:
Area = 7 cm × 4cm
= 28 sq. cm
Hence option (iv) is correct.
Question 2.
Which has more area?
(a) Postcard or Inland letter
(b) Blackboard or art sheet
(c) 10 rupee note or a 100 rupee note
(d) Handkerchief or Bedsheet.
Answer:
(a) Inland letter
(b) Blackboard
(c) 100 rupee note
(d) Bedsheet
Question 3.
Find the area in terms of unit squares.
Answer:
11 squares.
Answer:
4 squares.
Answer:
12 Squares.
Question 4.
Ramu has a paddy field which is in the shape of a rectangle. It has a length of 15 m and breadth of 8 m. If he has ploughed an area of 90 sq. m of the field, how much more area is to be ploughed?
Answer:
Length of paddy field = 15 m
Breadth of paddy field = 8 m
Area of paddy field = length × breadth
= 15 m × 8 m
= 120 m2.
He has ploughed = 90 sq. m.
Area left for ploughing= 120 sq. m – 90 sq. m
= 30 sq. m
Thus, 30 sq. m area is to be ploughed.
Question 5.
A square park is to be watered. If one side of the park is 5 m, find the area to be watered?
Answer:
One side of square park = 5 m
Area of square park = side × side
= 5 m × 5 m
= 25 sq. m
Question 6.
A wooden sheet is 15 m long and 6 m broad. It has to be painted on both sides. Find the cost of painting at ₹ 30 per square metre.
Answer:
Length of wooden sheet = 15 m
Breadth of wooden sheet = 6 m
Area = 15 m × 6 m
= 90 sq. m
∴ Area of both sides = 2 × 90 sq. m
= 180 sq.m
Painting cost of 1 sq. m = ₹ 30
∴ Painting cost of 180 sq. m = 30 × 180
= ₹ 5,400
Additional Questions
Question 1.
Tick (✓) the figure which has smaller surface.
Answer:
Question 2.
Find the area of these figure in term of unit area.
Answer:
(a) 11 squares
(b) 8 squares
(c) 4 squares
Question 3.
Find the area of the rectangles whose dimensions are given below.
(a) Length = 24m Breadth =15m
Answer:
Area of rectangle = Length × Breadth
= 24 m × 15 m
= 360 sq. m.
(b) Length = 15 m Breadth = 50cm
Answer:
Area of rectangle = Length × Breadth
Area of rectangle = 15 m ×x 0.50 m
= 7.50 sq. m
(c) Length = 170 cm Breadth = 50 cm
Answer:
Area of rectangle = Length × Breadth
Area of rectangle = 170 × 50
= 8500 sq. m
Question 4.
Find the area of shaded portion.
Answer:
(a) Area of shaded portion of rectangle = Area of outer rectangle – Area of inner rectangle
Area of outer rectangle = Length × Breadth
= 15 cm × 10 cm
= 150 sq. cm
Area of inner rectangle = Length × Breadth
= 9 cm × 4 cm
= 36 sq. cm
Area of shaded portion =150 sq. cm – 36 sq. cm
= 114 sq. cm
(b) Area of shaded portion of square = Area of outer square – Area of inner square
= (10 × 10) -(7 × 7)
= 100 sq. cm – 49 sq. cm
= 51 sq. cm
Question 5.
The length of a playground is 15 metres and breadth is 9 metres. Find the area of the playground.
Answer:
Area of playground = Length × Breadth
= 15 m × 9 m
= 135 sq. cm