Unit 18: Ratios
Section A: Introducing ratios
Short-answer questions
Instructions to students
• This section is designed to help improve your skills in calculating and simplifying ratios.
• Read the following questions and answer all of them in the spaces provided.
• No calculators.
• You will need to show all working.
• Reduce the ratios to the simplest or lowest form.
QUESTION 1
QUESTION 5
The number of teeth on gear cog 1 is 40. The number of
teeth on gear cog 2 is 20. What is the ratio of gear cog 1
to gear cog 2?
Three cogs have 80 : 60 : 20 teeth respectively. What is
the ratio?
Answer:
Answer:
4:3:1
2:1
QUESTION 6
QUESTION 2
Pulley A has a diameter of 600 mm and pulley B has a
diameter of 150 mm. What is the ratio of diameter A to B?
Answer:
A lathe has two pulleys that have diameters of 160 mm
and 200 mm respectively. What is the lowest ratio?
Answer:
4:5
4:1
QUESTION 7
QUESTION 3
Pulley A has a diameter of 480 mm and pulley B has a
diameter of 160 mm. What is the ratio of diameter
A to B?
The diameter of pulley A on a band saw is 320 mm.
Pulley B has a diameter of 160 mm and pulley C has a
diameter of 480 mm. What is the lowest ratio of the three
compared together?
Answer:
Answer:
3:1
2:1:3
QUESTION 4
QUESTION 8
A step-down transformer has 230 volts on winding
A and 25.5 volts on winding B. What is the ratio of
primary voltage to secondary voltage?
Three pulleys have different diameters: 180 mm, 160 mm
and 100 mm respectively. What is the comparative ratio?
Answer:
Answer:
9:8:5
9:1
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QUESTION 9
QUESTION 10
A step-down transformer has 680 turns on winding
A and 240 turns on winding B. What is the turns ratio
between the two windings?
A current transformer has 10 amperes on winding
A and 50 amperes on winding B. What is the ratio of
primary current to secondary current?
Answer:
Answer:
17 : 6
1:5
Section B: Applying ratios to the trade
Short-answer questions
Instructions to students
• This section is designed to help to improve your practical skills when working with ratios.
• Read the following questions and answer all of them in the spaces provided.
• No calculators.
• You will need to show all working.
QUESTION 1
The ratio of the teeth on cog 1 to cog 2 is 3 : 1. If cog 2
has 10 teeth, how many teeth will cog 1 have?
Answer:
30
QUESTION 4
QUESTION 2
The ratio of the teeth on cog 1 to cog 2 is 2 : 1. If cog 2
has 20 teeth, how many teeth will cog 1 have?
The ratio of the diameter of pulley A to pulley B is
2 : 1. If pulley A has a diameter of 300 mm, what will be
the diameter of pulley B?
Answer:
Answer:
40
150 mm
QUESTION 5
QUESTION 3
The ratio of the diameter of pulley A to pulley B is
4 : 2. If pulley A has a diameter of 400 mm, what will be
the diameter of pulley B?
The ratio of a transformer is 3:1. If there are 12 turns on
winding A, how many turns will there be on winding B?
Answer:
4
Answer:
200 mm
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QUESTION 6
QUESTION 9
A transformer has a ratio of 2:1 if the are 220 turns on
winding A, how many turns are there on winding B?
The ratio of windings in a transformer from winding
A to winding B is 4:3. If winding A has 160 turns, how
many turns are on winding B?
Answer:
Answer:
110
120
QUESTION 7
A motor drive has a ratio of teeth on cog A to cog B of
3 : 1. If the number of teeth on cog A is 21, how many
teeth will there be on cog B?
Answer:
QUESTION 10
The ratio of windings in a transformer from winding
A to winding B is 7:2. If winding A has 252 turns, how
many turns are on winding B?
Answer:
7
72
QUESTION 8
The ratio of teeth on cog A to cog B is 3 : 2. If the number
of teeth on cog A is 6, how many teeth will be on cog B?
Answer:
4
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