Practical Geometry - Solutions 2

CBSE Class –VII Mathematics
NCERT Solutions
Chapter 10 Practical Geometry (Ex. 10.2)
Question 1. Construct ΔXYZ in which XY = 4.5 cm, YZ = 5 cm and ZX = 6 cm.
Answer: To construct: ΔXYZ, where XY = 4.5 cm, YZ = 5 cm and ZX = 6 cm.

Steps of construction:
(a) Draw a line segment YZ = 5 cm.
(b) Taking Z as centre and radius 6 cm, draw an arc.
(c) Similarly, taking Y as centre and radius 4.5 cm, draw another arc which intersects first arc at point X.
(d) Join XY and XZ.
It is the required ΔXYZ.
Question 2. Construct an equilateral triangle of side 5.5 cm.
Answer: To construct: A ΔABC where AB = BC = CA = 5.5 cm

Steps of construction:
(a) Draw a line segment BC = 5.5 cm
(b) Taking points B and C as centers and radius 5.5 cm, draw arcs which intersect at point A.
(c) Join AB and AC.
It is the required ΔABC.
Question 3. Draw ΔPQR with PQ = 4 cm, QR = 3.5 cm and PR = 4 cm. What type of triangle is this?
Answer: To construction: ΔPQR, in which PQ = 4 cm, QR = 3.5 cm and PR = 4 cm.

Steps of construction:
(a) Draw a line segment QR = 3.5 cm.
(b) Taking Q as centre and radius 4 cm, draw an arc.
(c) Similarly, taking R as centre and radius 4 cm, draw an another arc which intersects first arc at P.
(d) Join PQ and PR.
It is the required isosceles ΔPQR.
Question 4. Construct ΔABC such that AB = 2.5 cm, BC = 6 cm and AC = 6.5 cm. Measure ∠B.
Answer: To construct :ΔABC in which AB = 2.5 cm, BC = 6 cm and AC = 6.5 cm.

Steps of construction:
(a) Draw a line segment BC = 6 cm.
(b) Taking B as centre and radius 2.5 cm, draw an arc.
(c) Similarly, taking C as centre and radius 6.5 cm, draw another arc which intersects first arc at point A.
(d) Join AB and AC.
(e) Measure angle B with the help of protractor.
It is the required ΔABC where ∠B =