A lamp and a bulb together cost £32.

The lamp costs £30 more than the bulb.

How much does the bulb cost?

• Steve Swarbrick, Balshaws Leyland
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• What a beautiful question.
All my classes assumed this was dead easy and that the answer was £2
• Ian Squires, New College Telford
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• Illuminating question! Used it to introduce some simple algebra :)
• Class 1M2, Lochend Community High School
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• This caused a big class discussion ...Thomas got it!!
• Y8 set 1 Mr Heeley's stars, NLC, Huddersfield
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• We think this was fab - shine a light!
It really lit up our day. Connor got it right, but everyone else was bambulbelled!
Keep it up Transum. Lamptastic!!
• Sion, Manning R.C Girls School
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• Very Good. It left my class puzzled and stunned when they realised the answer.
• Mr Sinclair, Oban High School, Scotland
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• A great puzzle. Wee jamie thought it was easy. The rest of the class all agreed eventually.
• Mrs Gocht, Dremy School
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• What a great puzzle we have most of my class did not know the answer for a long time but one smart bulb got it!
• Class 1.6, Brechin High School
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• This question was intriguing, so simple, yet so frustrating! We got the answer £2 into our heads and couldn't get it out. A light bulb went on in Campbell's head! More like this one, please!
• Class 1.4, Brechin High School
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• We automatically thought that the lamp was £30! That put us off the track. Three girls had a light bulb moment! We found a diagram useful.
• Mrs Morran, St. Fidelis Catholic Primary School
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• One of my class was very smart and worked it out some others still looked puzzled.
• Year 8, Welshpool High School
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• Jake was the only one to get it right. Everyone else said £2!
• Primary 7, Mosspark Primary Glasgow
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• We found this confusing.
• Nick G, Ireland
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• Whats the answer? This is driving me and my class nuts!

[Transum: The answers are available to Transum subscribers and are found lower down this page. You can subscribe by clicking here. Brazils or almonds?]
• Miss Karen, Hong Kong
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• We also had one smart student who got it!
The class thought it was tricky!
• News.com.au, Australia
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• Clive, Southampton
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• You have the same amount of money as your friend. How much should you give your friend so that he/she has got 10p more than you?
• Arush Sharma, Kolbe Catholic College
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• Let the bulb cost X dollars. Then the lamp will cost X+30. Then put it all into one equation:
X + X + 30 = 32
2X = 2
X = 1
So the bulb is \$1 and the lamp is \$31.

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.

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 This activity is suitable for students of mathematics all around the world. Use the button below to change the currency symbol used to make it more relevant to your students. You may wish to choose an unfamiliar currency to extend your students' experience.

Do you think the answer is £2?

If that is the case, the lamp must cost £30 more than that which is £32.

That means the total cost would be £34... wrong,
think again.

## Another

Here's another simple question that, for many people, does not have the intuitive answer.

In the final seconds of the marathon you overtake the person in second place. In what position do you finish?

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