20.3
Imperial units
Incorporating exercise:
20C
Homework:
Example:
20.3
20.3
Key words
inch (in)
foot (ft)
yard (yd)
mile (m)
ounce (oz)
pound (lb)
stone (st)
ton (T)
pint (pt)
gallon (gal)
Learning objective(s)
● convert one imperial unit to another
Prior knowledge
Pupils should know (or have written down) the links between the imperial units for:
length: 12 inches 1 foot, 3 feet 1 yard, 1760 yards 1 mile
weight: 16 ounces 1 pound, 14 pounds 1 stone, 2240 pounds 1 ton
capacity/volume: 8 pints 1 gallon
Starter
Do some mental divisions, by 3, 8 and 12, that have remainders. For example, 20 3 6 rem. 2, 20 8 2 rem.
4, 20 12 1 rem. 8.
Main teaching points
Unlike metric, there is no easy way to convert between imperial units – old fashioned rote learning by continually
telling and asking for the conversions throughout the lesson will help the pupils remember them.
Plenary
Tell the pupils that many very strange units were in use in olden days. For example, 8 furlongs 1 mile,
20 hundredweight (112 lb) 1 ton, 10 chains (22 yds) 1 furlong.
Many of these are still in use. Furlongs appear in horse racing distances. A chain is the length of a cricket pitch.
Ask pupils to research some old units on the Internet.
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Module 5: Algebra and Space, shape and measure
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Chapter 20 • Units • Homework 20.3
12 inches (in) 1 foot (ft)
16 ounces (oz) 1 pound (lb)
3 feet (ft) 1 yard (yd)
14 pounds (lb) 1 stone (st)
1760 yards (yd) 1 mile (m)
2240 pounds (lb) 1 ton (T)
8 pints (pt) 1 gallon (gal)
Fill in the gaps using the conversion factors given above.
1 1 ft ________________ in
9 1 lb ________________ oz
2 3 ft ________________ in
10 5 lb ________________ oz
3 24 in ________________ ft
11 48 oz ________________ lb
4 24 ft ________________ yd
12 1 st ________________ lb
5 1 mile ________________ yd
13 4480 lb ________________ T
6 10 miles ________________ yd
14
7 880 yd ________________ miles
15 1 gal ________________ pt
8 1 yd ________________ in
16 20 pt ________________ gal
Module 5: Algebra and Space, shape and measure
1
T ________________ lb
2
© HarperCollinsPublishers Ltd 2006
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Chapter 20 • Units • Worked example 20.3
Imperial units
1 Converting from one imperial unit to another
Fill in the gaps by converting between the given units.
a 5 feet ____inches
Solution
Big to small, so 12 inches 1 foot, so 12
5 12 60 inches
b 30 feet ____yards
Solution
Small to big, so 3 feet 1 yard, so 3
30 3 10 yards
c 3 miles ____yards
Solution
Big to small, so 1760 yards 1 mile, so 1760
3 1760 5280 yards
d 2 pounds ____ounces
Solution
Big to small, so 16 ounces 1 pound, so 16
2 16 32 ounces
e 7 pounds ____stone
Solution
Small to big, so 14 pounds 1 stone, so 14
1
7 14 stone
2
1
f
ton ____pounds
4
g 80 pints ____gallons
Solution
Small to big, so 8 pints 1 gallon, so 8
80 8 10 gallons
1
h
mile ____inches
2
Solution
Sometimes (not very often) you are given a
question such as, ‘How many inches in half a
mile?’ You do not have a conversion from miles to
inches, but you do know miles to yards, yards to
feet, and feet to inches, so do it in steps.
1
Step 1: mile ____yards
2
Big to small, so 1760 yards 1 mile, so 1760
1
1760 880 yards
2
Step 2: 880 yards ____feet
Big to small, so 3 feet 1 yard, so 3
880 3 2640 feet
Step 3: 2640 feet ____inches
Big to small, so 12 inches 1 foot, so 12
2640 12 31 680 inches
1
So: mile 31 680 inches
2
Solution
Big to small, so 2240 pounds 1 ton, so 2240
1
2240 560 pounds
4
Note:
When you are changing from a small unit to a big unit (for example, pints to gallons), you divide and, when you are
changing from a big unit to a small unit (for example, stone to pounds), you multiply.
© HarperCollinsPublishers Ltd 2006
Module 5: Algebra and Space, shape and measure