Mixed numbers and fractions of sets

Key idea: Name the whole before finding a fraction. A whole can be one object, a collection, or one unit in a mixed number.

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Enlarged diagram

Count the same-sized parts across wholes

Count quarters across all the strips. How many wholes do they make?

The marked amount is two wholes and three quarters. Each full strip is one whole. Count the marked quarters across all three strips.

Keep the quarter-sized parts

Each full strip is one equal-sized whole.

Equal-sized wholes, each split into four equal parts. Shading marks the amount.
Figure data

This table is included in print while it is open.

Equal parts in the picture
WholeParts in order
Strip Amarked; marked; marked; marked
Strip Bmarked; marked; marked; marked
Strip Cmarked; marked; marked; empty

A mixed number separates whole units from a fractional part. An improper fraction counts the parts together; its numerator is at least its denominator.

Write 2 3/4 as an improper fraction. Use a slash, as in 1/4.

Show answerHide answer

Each whole contains 4 quarters. Two wholes contain 8 quarters. The extra three make 11 quarters:

2 3/4 = 11/4.

The parts are still quarters. Changing the way we count does not change their size.

Explore: exchange the pieces

Select a whole and exchange it for four quarters. Repeat for the other whole. What stays the same?

What this checks

Exchange the starting pieces into the requested same-sized parts. Undo restores the earlier pieces.

The same amount

1
1
1/4
1/4
1/4

The same amount: 11/4 whole.

The starting amount.

Show solutionHide answer

Keep the quarter-sized parts

Each full strip is one equal-sized whole.

Equal-sized wholes, each split into four equal parts. Shading marks the amount.
Figure data

This table is included in print while it is open.

Equal parts in the picture
WholeParts in order
Strip Amarked; marked; marked; marked
Strip Bmarked; marked; marked; marked
Strip Cmarked; marked; marked; empty

Both wholes become eight quarters. With the three extra quarters, 2 3/4 = 11/4.

Make whole groups again

Write 17/5 as a mixed number. Make groups of five fifths. How many whole groups can you make? What is left?

Use a space between the whole and fraction, as in 1 1/4.

Show the regroupingHide answer

Seventeen fifths, grouped into wholes

Each full strip is one equal-sized whole.

Each complete strip holds five fifths. The remaining marked parts keep their size.
Figure data

This table is included in print while it is open.

Equal parts in the picture
WholeParts in order
Strip Amarked; marked; marked; marked; marked
Strip Bmarked; marked; marked; marked; marked
Strip Cmarked; marked; marked; marked; marked
Strip Dmarked; marked; empty; empty; empty

17 = 3 × 5 + 2, so 17/5 = 3 2/5. The remainder gives the fractional numerator. The denominator stays 5.

Make whole groups with nothing left

Write 20/5 as a whole number. Make groups of five fifths. Does any fractional part remain?

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20/5 = 4. There are no fifths left over. Do not add an extra whole.

Practise

Check your understanding 1

Move between the two forms

Choose how to count the parts

Write 4 1/6 as an improper fraction. Write 23/6 as a mixed number. Make or draw groups of sixths if you need them.

Why does four wholes and one sixth become 25 sixths?

Show answerHide answer

4 1/6 = 25/6 because 4 × 6 + 1 = 25.

23/6 = 3 5/6 because 23 = 3 × 6 + 5. Count the same sixth-sized parts in both directions.

Changing form and simplifying are separate decisions: 2 2/4 = 10/4 = 5/2. Simplify the fraction when the question asks for simplest form.

Do both ways of writing the fraction show the same amount?

Check your understanding 2

Check every whole

One record is wrong. Choose its row and write the correct answer.

Compare each written answer with its given task.
RowGiven taskWritten answer
A
3 1/4 as an improper fraction
4/4
B
2 2/3 as an improper fraction
8/3
Show the checksHide answer

A: 3 × 4 + 1 = 13, so 3 1/4 = 13/4.

B: 2 × 3 + 2 = 8, so 2 2/3 = 8/3. Keep this record.

Check your understanding 3

Keep all the leftover parts

One record is wrong. Choose its row and write the correct answer.

Compare each written answer with its given task.
RowGiven taskWritten answer
A
19/4 as a mixed or whole number
4 3/4
B
23/5 as a mixed or whole number
4 2/5
Show the checksHide answer

A: 19 = 4 × 4 + 3, so 19/4 = 4 3/4.

B: 23 = 4 × 5 + 3, so 23/5 = 4 3/5. Two fifths would lose one fifth.

Which counters make the whole set?

A set can be the whole

Find 3/8 of 24 counters. All 24 counters form the whole set. Share them into 8 equal groups, then select 3 groups.

Select groups, not single counters

Each row is an equal group. The selected and other groups together form the original set.

All 24 counters form one whole set. Each row is one of eight equal groups.
Figure data

This table is included in print while it is open.

Counters in words
SetCounters
Selected groupscounter; counter; counter; counter; counter; counter; counter; counter; counter
Other groupscounter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter

Show answerHide answer

One eighth is 24 ÷ 8 = 3 counters. Three eighths is 3 × 3 = 9 counters. Here the denominator counts equal groups; the numerator counts selected groups. Counting individual counters instead gives 9/24 = 3/8: the same selected part of the same whole.

Selecting only three counters would not select three eighths of this set.

Check your understanding 4

Name a fraction from the selected count

Keep the whole tray

A tray holds 18 counters. 6 are marked. What fraction of the whole tray is marked? What fraction is unmarked? Write each as a fraction; equivalent forms are welcome. Treat each counter as one equal part of the tray.

Both parts belong to the whole

The marked and unmarked counters are separate parts of the same tray. Include both parts when identifying the whole.

Both mats together form the whole tray. One dot is one counter.
Figure data

This table is included in print while it is open.

Counters in words
SetCounters
Markedcounter; counter; counter; counter; counter; counter
Unmarkedcounter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter
What is the denominator’s whole for the marked tray fraction?

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Marked: 6/18 = 1/3. Unmarked: 12/18 = 2/3. The two parts together make one whole tray.

6/12 compares the marked count with the unmarked count. It does not describe the marked part of the whole tray.

Check your understanding 5

Identify the whole set

Find a part without a picture

A box holds 35 beads. Two fifths are green. How many beads are green?

Help: find one fifth first

Show answerHide answer

14 beads: one fifth contains 35 ÷ 5 = 7 beads; two fifths contain 2 × 7 = 14. The 35 beads, including all colours, form the whole set.

How many stickers does one equal part stand for?

Let a bar stand for a large set

A shop has 240 stickers. 3/8 of them are star stickers. The rest are heart stickers. The shop then sells 45 heart stickers. How many heart stickers are left?

Use a bar to stand for all 240 stickers. Split it into 8 equal parts. Mark 3 parts for the star stickers.

One bar for all 240 stickers

Each full strip is one equal-sized whole.

The whole bar is all 240 stickers. Three of the eight equal parts are star stickers. The other five parts are heart stickers.
Figure data

This table is included in print while it is open.

Equal parts in the picture
WholeParts in order
All 240 stickersmarked; marked; marked; empty; empty; empty; empty; empty

Now use the second fact in the story. The 45 stickers sold are all heart stickers.

Two ways to find the heart stickersHide answer

One eighth is 240÷8 = 30 stickers.

Stars first: 3 × 30 = 90 star stickers, so 240-90 = 150 heart stickers.

Hearts straight from the bar: the heart stickers fill the other 5 parts, so 5 × 30 = 150.

Both ways give 150. Then 150-45 = 105 heart stickers are left.

Check: 90 + 150 = 240, and 105 + 45 = 150.

The 45 is not part of the fraction. Find the heart stickers first, then take away the 45 sold.

Check your understanding 6

Plan two steps with your own bar

A class collects 360 cans. 5/12 of them are drink cans. The rest are food cans. 70 food cans are dented. How many food cans are not dented?

Sketch a bar for all 360 cans before you calculate.

Help: use the bar one step at a time

Show answerHide answer

One twelfth is 360÷12 = 30 cans. Drink cans: 5 × 30 = 150. Food cans: 360-150 = 210, or 7 × 30 = 210. Food cans not dented: 210-70 = 140.

Check: 150 + 70 + 140 = 360 cans.

360-70 = 290 takes the dented cans from every can. The 70 dented cans are only food cans.

Are you finding a fraction of one group or the whole box?

Check which whole the fraction uses

Check your understanding 7

The same selected objects can name different fractions

A box holds 35 beads. 14 are green. 7 of the green beads have a star. The labelled mats show the parts of this one box.

Keep the selected seven; change the whole

The two green mats show all the green beads. All three mats show the whole box. The starred beads belong to both these groups.

One dot is one bead. The two green groups together form the green beads.
Figure data

This table is included in print while it is open.

Counters in words
SetCounters
Green, with a starcounter; counter; counter; counter; counter; counter; counter
Green, no starcounter; counter; counter; counter; counter; counter; counter
Other beadscounter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter; counter
Why can the same 7 starred beads be 1/2 and 1/5?

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Of the 14 green beads, 7/14 = 1/2 have a star. Of all 35 beads, 7/35 = 1/5 have a star.

The selected seven beads stay the same. The reference whole changes. Neither fraction means that only seven beads are in the box.

Check your understanding 8

Check the reference whole

One record is wrong. Choose its row and write the correct answer.

Compare each written answer with its given task.
RowGiven taskWritten answer
A
9 marked; 27 objects in all. Fraction marked
9/18
B
8 marked; 40 objects in all. Fraction marked
1/5
Show the checksHide answer

A: Nine marked objects belong to a whole set of 27: 9/27 = 1/3. The other 18 are only the unmarked part.

B: 8/40 = 1/5. Both marked and unmarked objects belong in the whole.

Check your understanding 9

Check the objects in the selected groups

One record is wrong. Choose its row and write the correct answer.

Compare each written answer with its given task.
RowGiven taskWritten answer
A
Number of objects in 3/8 of a set of 48
18
B
Number of objects in 2/7 of a set of 35
2
Show the checksHide answer

A: 48÷8 = 6 in each group, then 3 × 6 = 18 objects.

B: 35÷7 = 5 in each group, then 2 × 5 = 10 objects. The numerator 2 counts groups, not the objects in them.

Can the groups overlap?

A class has 30 pupils. Half are in a choir. One third of the whole class plays an instrument. How many are in each group? Is there enough information to find how many do neither?

What extra information would determine how many do neither?

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There are 15 choir pupils and 10 instrument players. We do not know how many belong to both groups, so we cannot find how many do neither.

If the groups are separate, 5 pupils do neither. If all ten instrument players are in the choir, 15 pupils do neither. Both fit what you know. You cannot choose one exact answer.

Before adding groups, check that the story says nobody belongs to both.

For a grown-up

Pip’s synthetic voice uses the University of Edinburgh’s Alba speech dataset, via Piper’s Alba voice, under CC BY 4.0. Audio is optional.

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