Frank Solutions for Chapter 20 Construction of Quadrilaterals Class 9 Mathematics ICSE

Exercise 20


1. Construct a quadrilateral ABCD in which

(i) AB = 4.6 cm, BD = 5 cm, AC = 6 cm, CD = 4.2 cm and ∠A = 90°

(ii) AB = 7.2 cm, BC = 5.8 cm, CD = 6.3 cm, AD = 4.3 cm and ∠A = 75°

(iii) AB = 4.8 cm, AC = 5.8 cm, AD = 3.6 cm, ∠A = 105° and ∠B = 60°

(iv) AD = AB = 5 cm, BC = 3.8 cm, CD = 3.5 cm and ∠BAD = 45°

Answer

(i) AB = 4.6 cm, BD = 5 cm, AC = 6 cm, CD = 4.2 cm and ∠A = 90°

Steps of Construction:

  1. Draw a line segment AB = 4.6 cm
  2. Taking A as centre, draw a ray making an angle of 900with AB
  3. With B as centre and radius equal to 5 cm cut an arc on the ray from A and mark it as point D
  4. With D as centre and radius 4.2 cm cut an arc on right side of AD
  5. Taking A as centre and radius 6 cm cut an arc which meets the arc from D at point C
  6. Now, join BC
  7. ABCD is the required quadrilateral

(ii) AB = 7.2 cm, BC = 5.8 cm, CD = 6.3 cm, AD = 4.3 cm and ∠A = 75°

Steps of Construction:

  1. Draw a line segment AB = 7.2 cm
  2. With A as centre draw rays X and Y to make angles 90° and 60° with AB. Then bisect the angle between them to make an angle of 75° with AB
  3. With A as centre and radius 4.3 cm cut an arc on line segment making 75° angle with AB and mark it as point D
  4. With D and B as centres and radii of 6.3 and 5.8 cm respectively, draw arcs cutting each other at point C
  5. Now, join DC and BC
  6. ABCD is the required quadrilateral

(iii) AB = 4.8 cm, AC = 5.8 cm, AD = 3.6 cm, ∠A = 105° and ∠B = 60°

Steps of Construction:

  1. Draw a line segment AB = 4.8 cm
  2. With A as centre draw rays X and Y to make angles 600and 900with AB produced. Then bisect the angle between them to make an angle of 1050 with AB
  3. With A as centre and radius 3.6 cm cut an arc on line segment making 1050angle with AB and name it as point D
  4. With B as centre draw a ray making an angle of 600with AB
  5. With A as centre and radius 5.8 cm cut an arc on the ray from B and mark the point as C
  6. Now, join BC and DC
  7. ABCD is the required quadrilateral

(iv) AD = AB = 5 cm, BC = 3.8 cm, CD = 3.5 cm and ∠BAD = 45°

Steps of Construction:

  1. Draw a line segment AB = 5 cm
  2. With A as centre draw an angle of 90° and bisect it to form ∠BAD = 45°
  3. With A as centre and radius 5 cm cut an arc on the ray making an angle of 45° with AB and name it as point D
  4. With D and B as centre and radii as 3.5 cm and 3.8 cm respectively draw arcs intersecting each other at point C
  5. Now, join DC and BC
  6. ABCD is the required quadrilateral


2. Construct a trapezium ABCD in which

(i) AB = 3.5 cm, BC = 6 cm, CD = 3.5 cm, AD = 4.4 cm and AD || BC

(ii) AB = 4.6 cm, BC = 6.4 cm, CD = 5.6 cm, ∠B = 60° and AD || BC

Answer

(i) AB = 3.5 cm, BC = 6 cm, CD = 3.5 cm, AD = 4.4 cm and AD || BC

Steps of Construction:

  1. Draw BC of length 6 cm
  2. From BC, cut BE = 4.4 cm
  3. Draw a triangle DEC, such that DE = AB = 3.5 cm and CD = 3.5 cm
  4. With B and D as centres and radii 3.5 cm and 4.4 cm respectively, draw arcs cutting each other at point A
  5. Now, join AB and AD
  6. Thus, ABCD is the required trapezium

(ii) AB = 4.6 cm, BC = 6.4 cm, CD = 5.6 cm, ∠B = 60° and AD || BC

Steps of Construction:

  1. Draw BC of length 6.4 cm
  2. With B as centre, draw an angle of 60° and cut an arc with radius 4.6 cm. Name this point as A
  3. From point A, draw a line segment parallel to BC
  4. With C as centre and radius 5.6 cm cut an arc on the line segment parallel to BC. Name this point as D
  5. Join CD
  6. Thus, ABCD is the required trapezium


3. Construct a parallelogram ABCD in which AB = 4.5 cm, ∠A = 105° and the distance between AB and CD is 3.2 cm

Answer

Steps of Construction:

  1. Draw a line segment AB = 4.5 cm
  2. At B, draw BX perpendicular to AB
  3. From B, cut BR = 3.2 cm on BX which is the distance between AB and CD
  4. Through R, draw a line perpendicular to BX to get QR parallel to AB
  5. Taking A as centre, draw a ray AP making an angle of 105° with AB and meeting QR at point D
  6. Taking B as centre, draw an arc with radius = AD on QR and name it as point C
  7. Now, join BC
  8. ABCD is the required parallelogram


4. Construct a rhombus whose perimeter is 16 cm and BD = 6.2 cm

Answer

The length of all the sides of rhombus is equal

Therefore,

Perimeter = side×4

Side = perimeter/4

Side = 16/4

We get,

Side = 4 cm

Steps of Construction:

  1. Draw a line segment BD = 6.2 cm
  2. Taking B as centre and radius 4 cm, draw two arcs one above BD and the other below BD
  3. Taking D as centre and radius 4 cm draw two arcs one above BD and the other below BD intersecting the previous arcs drawn in step 2 at points A and C respectively
  4. Now, join AB, BC, CD and AD
  5. ABCD is the required rhombus


5. Construct a rhombus whose diagonals AC = 7.4 cm and BD = 6 cm

Answer

The diagonals of a rhombus bisect each other

Steps of Construction:

  1. Draw a line segment AC = 7.4 cm
  2. Draw perpendicular bisector to AC which cuts AC at point O
  3. From this perpendicular cut OD and OB such that OD = OB = (1/2) BD = (1/2)×6 cm = 3 cm
  4. Now, join AB, BC, CD and AD
  5. ABCD is the required rhombus


6. Construct a rhombus whose side AB = 5 cm and diagonal AC = 6 cm. Measure DB and AD.

Answer

In rhombus all sides are equal

Steps of Construction:

  1. Draw AC of length 6 cm
  2. With A as centre and radius 5 cm, draw two arcs one above AC and the other below AC
  3. Taking C as centre and radius 5 cm draw two arcs one above AC and the other below AC intersecting the previous arcs of Step 2 at points B and D respectively
  4. Now, join AB, BC, CD and AD
  5. ABCD is the required rhombus
  6. On measuring we get, AD = 5 cm and DB = 8 cm


7. Construct a square with each side 4.3 cm

Answer

Sides of square are equal

Steps of Construction:

  1. Draw PQ of length 4.3 cm
  2. Construct ∠PQT = 90° at Q
  3. From QT cut off QR = 4.3 cm
  4. From P and R, draw two arcs of radii 4.3 cm each to cut each other at point S
  5. Now, join PS and RS
  6. PQRS is the required square


8. Construct a square ABCD with AC = 6.5 cm

Answer

The diagonals of a square are equal and bisect each other

Steps of Construction:

  1. Draw AC of length 6.5 cm
  2. Draw perpendicular bisector to AC which cuts AC at point O
  3. From this perpendicular cut OD and OB such that OD = OB = (1/2) BD = (1/2)×6.5 = 3.25 cm
  4. Now, join AB, BC, CD and AD
  5. ABCD is the required square


9. Construct a square with perimeter = 18 cm

Answer

Sides of square are equal

Perimeter = 4×side

Side = perimeter/4

⇒ Side = 18/4

We get,

Side = 4.5 cm

Steps of Construction:

  1. Draw PQ of length 4.5 cm
  2. Construct ∠PQT = 90° at Q
  3. From QT cut off QR = 4.5 cm
  4. From P and R, draw two arcs of radii 4.5 cm each to cut each other at point S
  5. Now, join PS and RS
  6. PQRS is the required square


10. Construct a square whose area is 25 sq. cm.

Answer

Steps of Construction:

  1. Draw PQ of length 5 cm
  2. Construct ∠PQT = 90° at Q
  3. From QT cut off QR = 5 cm
  4. From P and R, draw two arcs of radii 5 cm each to cut each other at point S
  5. Now, join PS and RS
  6. PQRS is the required square


11. Construct a rectangle ABCD with one diagonal AC = 5.8 cm and the acute angle between the diagonals is equal to 45°

Answer

Steps of Construction:

  1. Draw AC of length 5.8 cm and locate its midpoint O
  2. Draw line BOD such that ∠DOC = 45° and OB = OD = (1/2) BD = (1/2)°5.8 cm = 2.9 cm
  3. Now, join AB, BC, CD and DA
  4. Thus ABCD is the required rectangle


12. Construct a rectangle ABCD with perimeter 18 cm and AB = 6 cm

Answer

Opposite sides of a rectangle are equal

Hence,

AB = CD and BC = DA

Perimeter of rectangle = AB + BC + CD + DA

⇒ 18 cm = AB + BC + AB + BC

⇒ 18 cm = 6 + BC + 6 + BC

⇒ (18 – 12) cm = 2BC

We get,

BC = 3 cm

Hence,

AB = CD = 6 cm and BC = DA = 3 cm

Steps of Construction:

  1. Draw AB = 6 cm
  2. On A and B draw perpendiculars AX and BY to AB
  3. Taking A and B as centres and radii 3 cm draw arcs on AX and BY. Mark them as points D and C respectively
  4. Now, join CD
  5. Therefore, ABCD is the required rectangle


13. Construct a rectangle ABCD, AB = 6 cm, ∠CAB = 30°

Answer

Steps of Construction:

  1. Draw AB = 6 cm
  2. On A and B draw perpendiculars AX and BY to AB
  3. Taking A as centre, draw a line making an angle of 30° with AB and intersecting BY at point C
  4. With A as centre and radius = BC cut an arc on AX. Name it as point D
  5. Join CD
  6. Hence, ABCD is the required rectangle


14. Construct a regular hexagon of side 3.5 cm

Answer

Steps of Construction:

  1. Draw a circle with radius of length 3.5 cm
  2. Take a point A on the circle. With A as centre and radius 3.5 cm cut the circle at B and from B with radius 3.5 cm cut the circle at C and so on
  3. Now, join AB, BC, CD, DE, EF and AF
  4. Therefore, ABCDEF is the required regular hexagon


15. Construct a regular hexagon of side 4 cm. 

Answer

Steps of Construction:

  1. Draw AB of length 4 cm
  2. With centres A and B and radius 4 cm draw arcs to cut each other at O
  3. Taking O as centre and the radius 4 cm cut the arc drawn in step 2 at C and F. Now, join AF and BC
  4. With centres C and F and radius 4 cm cut the arcs drawn in step 3 at D and E. Then join CD, DE and EF
  5. Thus ABCDEF is the required regular hexagon


16. Construct a parallelogram ABCD. Given:

(i) AB = 5.5 cm, BC = 3.5 cm, ∠B = 75°

(ii) AB = 3.5 cm, AC = 4 cm and BD = 5.2 cm

Answer

(i) AB = 5.5 cm, BC = 3.5 cm, ∠B = 75°

(ii) AB = 3.5 cm, AC = 4 cm and BD = 5.2 cm


17. Construct a parallelogram PQRS in which PQ = 6.4 cm, QR = 4 cm and the distance between PQ and SR is 3 cm.

Answer


18. Construct a rhombus ABCD, AB = 3.8 cm and ∠A = 60°. Measure AC.

Answer


19. Construct a parallelogram PQRS in which PQ = 6.4 cm, QR = 4 cm and the distance between PQ and SR is 3 cm.

Answer


20. (a) Construct a rectangle PQRS, when its Area = 21 cm2 and length = 4.2 cm

(b) Construct a rectangle PQRs, when its Area = 33.8 cm2 and breadth = 6.5 cm

Answer

(a)

(b)

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