Answers to Coursebook exercises

Answers to Coursebook exercises
5 Angles
F Exercise 5.1
1
a
b
Check students’ sketches.
angle at B
c BAC or CAB; ACB or BCA
2 a
acute
b reflex
c right
d obtuse
e reflex
f reflex
3 a
obtuse
b acute
c reflex
d reflex
e acute
f obtuse
4 a
45°
b 270°
c 315°
d 315°
5 a
120°
b 120°
c 60°
d 240°
e 300°
6 a
60°
b 120°
c 270°
d 30°
e 240°
c 220°
h 246°
d 325°
e 164°
f 300°
F Exercise 5.2
1
a
f
55°
33°
b 130°
g 292°
2 Check students’ drawings.
3 a x = 80, y = 235, z = 45
b A whole turn is 360°.
4 a r = 307, s = 283, t = 310
b Check students’ working.
c The interior angles of an equilateral triangle are 60°, the exterior angles are all
300°, and 3 × 300 = 900.
5 a 235°, 323° and 342°
b Not possible
F Exercise 5.3
1
a
64°
b 125°
c 96°
d 56°
2 a
110°
b 168°
c 204°
d 228°
3 a
120°
b 72°
4 a
74°
b 62°
c 117°
5 a
115°
b 155°
c 61°
b 223°
c 53°
6 110°
7 a
92°
8 It is a rectangle or a square.
9 They add up to more than 360°.
10 70°
Copyright Cambridge University Press 2012
Cambridge Checkpoint Mathematics 7
1
Unit 5
Answers to Coursebook exercises
F Exercise 5.4
1 Angle APC + angle APD = 180° because they are angles on a straight line. So angle APC = 180° – angle APD.
Angle APD + angle DPB = 180°. So angle DPB = 180° – angle APD.
Hence angle APC = angle DPB.
2 a = 73. It adds up to 180 with 61 and 46. b = 61, vertically opposite angles. c = 46, vertically opposite angles.
d = 73, vertically opposite a.
3 a = b = 77; c = 103
4 The angles at A are the three angles of the triangle. They make a straight line.
5 Each one is 70°.
6 75°
7 The third angle is 72°. The triangle is isosceles. Two sides are the same length.
End of unit review
1 a70°
b45°
2 a Check students’ drawings.
b i acute
ii obtuse
3 a i60° ii161°
b Triangles iii and iv
4 a78°
b95°
c260°
iii reflex
iii72°
d105°
iv reflex
iv21°
c129°
5 a No. They will add up to less than 360°
c Yes. 200°, 40°, 40° and 80° is one example.
b Yes. 100°, 100°, 100° and 60° is one example.
d No. They will add up to more than 360°.
6 s = 75, t = 105
2
Cambridge Checkpoint Mathematics 7
Copyright Cambridge University Press 2012

Download Report