Worked examples
The question
Question: Adult tickets cost $9 and child tickets cost $6.
A cinema sold 3 times as many child tickets as adult tickets.
It made $540.
How many of each ticket did it sell?
1 Find what we know
What do we know?
Two kinds: adult tickets cost $9 each, child tickets cost $6 each.
There are 3 times as many child tickets as adult tickets.
All the money: $540.
What do we want?
How many adult tickets, and how many child tickets.
2 Name the unknown
We know the child tickets from the adult tickets.
So we start with the adult tickets.
We call how many there are x.
x = adult tickets
There are 3 times as many child tickets as adult tickets.
3 times x: 3x.
3x = child tickets
Careful!
There are 3 times as many child tickets as adult tickets.
So the child tickets are 3x, not the adult tickets.
Careful: not 3x = adult tickets ✗
like: 10 adult → 3 × 10 = 30 child
Let's put it in a table: how many, the price, and the money.
Adult tickets: x of them, $9 each.
Child tickets: 3x of them, $6 each.
Money = how many times the price.
9 times x is 9x.
6 times all of 3x is 6(3x).
We keep 3x together in brackets.
The total: $540 in all.
3 Write the equation
In words: the adult money plus the child money makes all the money.
9x + 6(3x) = 540
So the equation is 9x + 6(3x) = 540.
Now we solve it.
9x + 6(3x) = 540
4 Open the brackets
The 6 in front of the bracket multiplies every part inside.
So we write 6 times each part.
9x + 6 × 3x = 540
Work out each multiplication.
9x + 18x = 540
5 Group like terms
Terms are the parts between the + and − signs.
Like terms are the same kind: same letters, same powers.
All the x terms go together.
9x + 18x = 27x.
9x + 18x = 27x
Now we have 27x = 540.
27x = 540
6 Remove the 27
27x means 27 times x.
We want just x.
To remove times 27, we divide by 27.
We do it on both sides, so they stay equal.
27x27 = 54027
27 divided by 27 is 1.
So just x is left.
540 divided by 27 is 20.
54027 = 20
So x = 20!
x = 20
7 Answer the question
Child tickets: 3x.
3 × 20 = 60.
3x = 3 × 20 = 60
So 20 adult tickets and 60 child tickets.
8 Check
Let's check in the story.
3 times 20 is 60: 3 times as many, like the story says.
3 × 20 = 60
The money: $180 plus $360 makes $540, like the story says.
20 × $9 + 60 × $6 = $180 + $360 = $540
Does it make sense?
Both are whole numbers, not below 0.
That fits tickets.
So the answer is right!
makes sense: 20 and 60: whole, 0 or more
Let's look back.
First: find what we know.
Then: name the unknown.
Then: write the equation.
Then: solve it.
Then: answer the question.
Last: check.
▶ Watch it solved
The question
Question: Adult tickets cost $6 and child tickets cost $4.
A cinema sold 15 fewer child tickets than adult tickets.
It made $540.
How many of each ticket did it sell?
1 Find what we know
What do we know?
Two kinds: adult tickets cost $6 each, child tickets cost $4 each.
There are 15 fewer child tickets than adult tickets.
All the money: $540.
What do we want?
How many adult tickets, and how many child tickets.
2 Name the unknown
We know the child tickets from the adult tickets.
So we start with the adult tickets.
We call how many there are x.
x = adult tickets
15 fewer: x − 15.
x − 15 = child tickets
Careful!
There are 15 fewer child tickets than adult tickets.
So the − 15 goes with the child tickets, not the adult tickets.
Careful: not x − 15 = adult tickets ✗
Let's put it in a table: how many, the price, and the money.
Adult tickets: x of them, $6 each.
Child tickets: x − 15 of them, $4 each.
Money = how many times the price.
6 times x is 6x.
4 times all of x − 15 is 4(x − 15).
We keep x − 15 together in brackets.
The total: $540 in all.
3 Write the equation
In words: the adult money plus the child money makes all the money.
6x + 4(x − 15) = 540
So the equation is 6x + 4(x − 15) = 540.
Now we solve it.
6x + 4(x − 15) = 540
4 Open the brackets
The 4 in front of the bracket multiplies every part inside.
So we write 4 times each part.
6x + 4 × x + 4 × (−15) = 540
Work out each multiplication.
6x + 4x − 60 = 540
5 Group like terms
Terms are the parts between the + and − signs.
Like terms are the same kind: same letters, same powers.
All the x terms go together.
6x + 4x = 10x.
6x + 4x = 10x
Now we have 10x − 60 = 540.
10x − 60 = 540
We want x by itself.
Two things are stuck to x: times 10 and − 60.
The − 60 is on the outside, so it comes off first.
Then the times 10.
6 Remove the − 60
To remove − 60, we add 60.
We do it on both sides, so they stay equal.
10x − 60 + 60 = 540 + 60
− 60 and + 60 make zero.
Cross them out.
540 + 60 = 600.
540 + 60 = 600
Now we have 10x = 600.
10x = 600
7 Remove the 10
10x means 10 times x.
We want just x.
To remove times 10, we divide by 10.
We do it on both sides, so they stay equal.
10x10 = 60010
10 divided by 10 is 1.
So just x is left.
600 divided by 10 is 60.
60010 = 60
So x = 60!
x = 60
8 Answer the question
Child tickets: x − 15.
60 − 15 = 45.
x − 15 = 60 − 15 = 45
So 60 adult tickets and 45 child tickets.
9 Check
Let's check in the story.
45 is 15 fewer than 60, like the story says.
60 − 45 = 15
The money: $360 plus $180 makes $540, like the story says.
60 × $6 + 45 × $4 = $360 + $180 = $540
Does it make sense?
Both are whole numbers, not below 0.
That fits tickets.
So the answer is right!
makes sense: 60 and 45: whole, 0 or more
Let's look back.
First: find what we know.
Then: name the unknown.
Then: write the equation.
Then: solve it.
Then: answer the question.
Last: check.
▶ Watch it solved
The question
Question: Adult tickets cost $8 and child tickets cost $6.
A cinema sold 3 times as many child tickets as adult tickets.
It made $650.
How many of each ticket did it sell?
1 Find what we know
What do we know?
Two kinds: adult tickets cost $8 each, child tickets cost $6 each.
There are 3 times as many child tickets as adult tickets.
All the money: $650.
What do we want?
How many adult tickets, and how many child tickets.
2 Name the unknown
We know the child tickets from the adult tickets.
So we start with the adult tickets.
We call how many there are x.
x = adult tickets
There are 3 times as many child tickets as adult tickets.
3 times x: 3x.
3x = child tickets
Careful!
There are 3 times as many child tickets as adult tickets.
So the child tickets are 3x, not the adult tickets.
Careful: not 3x = adult tickets ✗
like: 10 adult → 3 × 10 = 30 child
Let's put it in a table: how many, the price, and the money.
Adult tickets: x of them, $8 each.
Child tickets: 3x of them, $6 each.
Money = how many times the price.
8 times x is 8x.
6 times all of 3x is 6(3x).
We keep 3x together in brackets.
The total: $650 in all.
3 Write the equation
In words: the adult money plus the child money makes all the money.
8x + 6(3x) = 650
So the equation is 8x + 6(3x) = 650.
Now we solve it.
8x + 6(3x) = 650
4 Open the brackets
The 6 in front of the bracket multiplies every part inside.
So we write 6 times each part.
8x + 6 × 3x = 650
Work out each multiplication.
8x + 18x = 650
5 Group like terms
Terms are the parts between the + and − signs.
Like terms are the same kind: same letters, same powers.
All the x terms go together.
8x + 18x = 26x.
8x + 18x = 26x
Now we have 26x = 650.
26x = 650
6 Remove the 26
26x means 26 times x.
We want just x.
To remove times 26, we divide by 26.
We do it on both sides, so they stay equal.
26x26 = 65026
26 divided by 26 is 1.
So just x is left.
650 divided by 26 is 25.
65026 = 25
So x = 25!
x = 25
7 Answer the question
Child tickets: 3x.
3 × 25 = 75.
3x = 3 × 25 = 75
So 25 adult tickets and 75 child tickets.
8 Check
Let's check in the story.
3 times 25 is 75: 3 times as many, like the story says.
3 × 25 = 75
The money: $200 plus $450 makes $650, like the story says.
25 × $8 + 75 × $6 = $200 + $450 = $650
Does it make sense?
Both are whole numbers, not below 0.
That fits tickets.
So the answer is right!
makes sense: 25 and 75: whole, 0 or more
Let's look back.
First: find what we know.
Then: name the unknown.
Then: write the equation.
Then: solve it.
Then: answer the question.
Last: check.
▶ Watch it solved