Ratios (GCSE Maths)
Skill Check
Alex and Bob share money in the ratio 3 : 8.
Bob receives ยฃ35 more than Alex.
How much money do they share in total?
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Step 1 ย ยทย Find the difference in ratio parts
The ratio of Alex's share to Bob's share is $3 : 8$.
Step 2 ย ยทย Find the value of a single part
- We are told that this difference of $5$ parts is equal to $ยฃ35$.
- To find the value of $1$ part, divide the monetary difference by the difference in parts.
Step 3 ย ยทย Find the total number of parts
Add the numbers in the ratio together to find the total shares.
Step 4 ย ยทย Calculate the total amount of money
Multiply the total number of parts by the value of a single part.
Final Answer
$ยฃ77$
A piece of wood is 240 cm long.
It is cut into three pieces in the ratio 2 : 3 : 7.
How long is the shortest piece?
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Step 1 ย ยทย Find the total number of parts
Add the numbers in the ratio together to find out how many equal parts the wood is divided into in total.
Step 2 ย ยทย Find the length of a single part
Divide the total length of the wood by the total number of parts.
Step 3 ย ยทย Calculate the length of the shortest piece
- The shortest piece corresponds to the smallest number in the ratio, which is $2$.
- Multiply the length of one part by $2$.
Final Answer
$40\text{ cm}$
The angles in a triangle are in the ratio 1 : 2 : 3.
Calculate the size of the largest angle.
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Step 1 ย ยทย State the total sum of angles
The interior angles of any triangle always add up to $180^\circ$.
Step 2 ย ยทย Find the total number of parts in the ratio
Add the numbers in the ratio together to find the total number of shares.
Step 3 ย ยทย Find the value of a single part
Divide the total degrees by the total number of parts.
Step 4 ย ยทย Calculate the largest angle
- The largest angle corresponds to the largest number in the ratio, which is $3$.
- Multiply the value of one part by $3$.
Final Answer
$90^\circ$
The ratio of cats to dogs in a shelter is 4 : 5.
There are 24 cats.
How many dogs are there?
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- Ensure all calculation steps are legible.
- Upload below for AI Tutor analysis.
Step 1 ย ยทย Identify the parts of the ratio
- The ratio of cats to dogs is given as $4 : 5$.
- This means for every $4$ parts of cats, there are $5$ parts of dogs.
Step 2 ย ยทย Find the value of a single part
We are told there are $24$ cats, which corresponds to the $4$ parts in our ratio. To find the value of $1$ part, divide the total number of cats by $4$.
So, $1\text{ part} = 6\text{ animals}$.
Step 3 ย ยทย Calculate the number of dogs
The dogs represent $5$ parts of the ratio. Multiply the value of a single part by $5$.
Final Answer
$30\text{ dogs}$
Simplify the ratio 45 : 60.
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Step 1 ย ยทย Find a common factor
- Look for the highest number that divides evenly into both $45$ and $60$.
- The Highest Common Factor (HCF) is $15$.
- (Tip: If you don't spot $15$ right away, you can start by dividing both numbers by a smaller common factor like $5$ or $3$, and then repeat the process with the new numbers).
Step 2 ย ยทย Divide both sides by the common factor
Final Answer
$3 : 4$
Problem Solving
Divide 1440 in the ratio 3 : 5 : 4.
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Step 1 ย ยทย Find the total number of parts
Add the numbers in the ratio together to determine how many equal parts the total amount is divided into:
Step 2 ย ยทย Find the value of a single part
Divide the total amount ($1440$) by the total number of parts ($12$):
Step 3 ย ยทย Calculate the value for each part
Multiply the value of one part by each number in the original ratio:
- First part: $3 \times 120 = 360$
- Second part: $5 \times 120 = 600$
- Third part: $4 \times 120 = 480$
Final Answer
$360,\ 600,\ 480$
Divide 1200 in the ratio 1 : 2 : 3.
- Take a clear photo of your handwritten work.
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Step 1 ย ยทย Find the total number of parts
Add the numbers in the ratio together to determine how many equal parts the total amount is divided into:
Step 2 ย ยทย Find the value of a single part
Divide the total amount ($1200$) by the total number of parts ($6$):
Step 3 ย ยทย Calculate the value for each part
Multiply the value of one part by each number in the original ratio:
- First part: $1 \times 200 = 200$
- Second part: $2 \times 200 = 400$
- Third part: $3 \times 200 = 600$
Final Answer
$200,\ 400,\text{ and } 600$
Divide 840 in the ratio 3 : 4 : 5.
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Step 1 ย ยทย Find the total number of parts
Add the numbers in the ratio together to determine how many equal parts the total amount is divided into.
Step 2 ย ยทย Find the value of a single part
Divide the total amount ($840$) by the total number of parts ($12$).
Step 3 ย ยทย Calculate the value for each part
Multiply the value of one part by each number in the original ratio:
- First part: $3 \times 70 = 210$
- Second part: $4 \times 70 = 280$
- Third part: $5 \times 70 = 350$
Final Answer
$210, 280, \text{ and } 350$
Divide 450 in the ratio 4 : 5.
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Step 1 ย ยทย Find the total number of parts
Add the numbers in the ratio together to determine how many equal parts the total amount is divided into.
Step 2 ย ยทย Find the value of a single part
Divide the total amount ($450$) by the total number of parts ($9$).
Step 3 ย ยทย Calculate the value for each side of the ratio
Multiply the value of one part by each number in the original ratio.
Final Answer
$200 \text{ and } 250$
Divide 64 in the ratio 5 : 3.
- Take a clear photo of your handwritten work.
- Ensure all calculation steps are legible.
- Upload below for AI Tutor analysis.
Step 1 ย ยทย Find the total number of parts
Add the numbers in the ratio together to determine how many equal parts the total amount is divided into.
Step 2 ย ยทย Find the value of a single part
Divide the total number ($64$) by the total number of parts ($8$).
Step 3 ย ยทย Calculate the value for each side
Multiply the value of one part by each number in the original ratio.
Final Answer
$40\text{ and }24$
Exam-Style Questions
A business makes a profit of ยฃ4,500.
It donates 20% of the profit to charity, and the two partners split the remaining profit in the ratio 5 : 4.
How much does the partner with the larger share receive?
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Step 1 ย ยทย Calculate the remaining profit
First, find out how much is donated to charity. $20\%$ of $ยฃ4{,}500$ is $ยฃ900$:
Subtract this from the total profit to find the remaining amount to be split:
(Alternatively, you can just calculate $80\%$ of $ยฃ4{,}500$ directly).
Step 2 ย ยทย Find the total number of parts
Add the numbers in the ratio together to determine how many equal parts the remaining profit is divided into:
Step 3 ย ยทย Find the value of a single part
Divide the remaining profit ($ยฃ3{,}600$) by the total number of parts ($9$):
Step 4 ย ยทย Calculate the larger share
- The partner with the larger share corresponds to the number $5$ in the ratio.
- Multiply the value of one part by $5$:
Final Answer
$ยฃ2{,}000$
In a sports club, the ratio of swimmers to runners is 3 : 4, and the ratio of runners to cyclists is 2 : 5.
What is the ratio of swimmers to runners to cyclists?
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Step 1 ย ยทย Identify the common group
The "runners" appear in both given ratios, linking the swimmers and the cyclists together.
Step 2 ย ยทย Line up the ratios
Look at the numbers representing the runners in both ratios:
Step 3 ย ยทย Make the common parts equal
Find a common multiple for the runner parts ($4$ and $2$). The lowest common multiple is $4$.
- The first ratio already has $4$ for runners, so it stays the same ($3 : 4$).
- To make the runners $4$ in the second ratio, multiply both sides of that ratio by $2$:
Step 4 ย ยทย Combine the ratios
Now that the runners are represented by $4$ in both, you can merge them into a single three-part ratio:
Final Answer
$3 : 4 : 10$
A bowl contains apples and oranges in the ratio 2 : 3.
If 4 more apples are added to the bowl, the new ratio of apples to oranges becomes 1 : 1.
How many oranges are in the bowl?
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Step 1 ย ยทย Set up the initial ratio with a variable
Let the initial number of apples be $2x$ and the number of oranges be $3x$.
Step 2 ย ยทย Create an equation based on the change
- We are told that 4 apples are added, so the new amount of apples is $2x + 4$.
- The number of oranges stays the same at $3x$.
- The new ratio of apples to oranges is $1 : 1$, which means the number of apples now equals the number of oranges.
We can write this as an equation:
Step 3 ย ยทย Solve for $x$
Subtract $2x$ from both sides of the equation to find the value of $x$:
Step 4 ย ยทย Calculate the number of oranges
- The question asks for the number of oranges, which is represented by $3x$.
- Substitute $x = 4$ into the expression:
Final Answer
$12\text{ oranges}$
A landscaper mixes sand, gravel, and cement in the ratio 4 : 5 : 2.
If they use 150 kg of gravel for a project, how much sand and cement do they need?
- Take a clear photo of your handwritten work.
- Ensure all calculation steps are legible.
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Step 1 ย ยทย Identify the parts of the ratio
- The ratio of sand to gravel to cement is $4 : 5 : 2$.
- This means gravel represents $5$ parts of the total mixture.
Step 2 ย ยทย Find the value of a single part
- We are told that the $5$ parts of gravel equal $150\text{ kg}$.
- To find the value of $1$ part, divide the total weight of the gravel by its corresponding ratio number.
Step 3 ย ยทย Calculate the amount of sand
- Sand represents $4$ parts of the ratio.
- Multiply the value of a single part by $4$.
Step 4 ย ยทย Calculate the amount of cement
- Cement represents $2$ parts of the ratio.
- Multiply the value of a single part by $2$.
Final Answer
$120\text{ kg}\text{ sand, } 60\text{ kg}\text{ cement}$
The ratio of adult tickets to child tickets sold at a theme park is 5 : 2.
If 120 more adult tickets were sold than child tickets,
what is the total number of tickets sold?
- Take a clear photo of your handwritten work.
- Ensure all calculation steps are legible.
- Upload below for AI Tutor analysis.
Step 1 ย ยทย Find the difference in ratio parts
The ratio of adult to child tickets is $5 : 2$.
Step 2 ย ยทย Find the value of a single part
- We are told that this difference of $3$ parts is equal to $120$ tickets.
- To find the value of $1$ part, divide the numerical difference by the difference in parts.
Step 3 ย ยทย Find the total number of parts
Add the numbers in the ratio together to find the total shares.
Step 4 ย ยทย Calculate the total number of tickets
Multiply the total number of parts by the value of a single part.
Final Answer
$280\text{ tickets}$
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