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Answer: 1
Using proportion
4.5 litres of antifreeze in new mixture
1 more litre needed
Using algebra
Let the extra volume of antifreeze required be $x$ litres. Initially, there are 3.5 litres of antifreeze in the solution. So $3.5+x=0.3(14+x)$, that is, $35+10x=42+3x$, so $x=1$.
Antifreeze
Age 14 to 16
ShortChallenge Level 
Answer: 1
Using proportion
4.5 litres of antifreeze in new mixture
1 more litre needed
Using algebra
Let the extra volume of antifreeze required be $x$ litres. Initially, there are 3.5 litres of antifreeze in the solution. So $3.5+x=0.3(14+x)$, that is, $35+10x=42+3x$, so $x=1$.
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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