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 cm^{2} – 30 cm^{2}

= 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 m^{2}.

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