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
•
• What a beautiful question.
All my classes assumed this was dead easy and that the answer was £2
• Ian Squires, New College Telford
•
• Illuminating question! Used it to introduce some simple algebra :)
• Class 1M2, Lochend Community High School
•
• This caused a big class discussion ...Thomas got it!!
• Y8 set 1 Mr Heeley's stars, NLC, Huddersfield
•
• 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
•
• Very Good. It left my class puzzled and stunned when they realised the answer.
• Mr Sinclair, Oban High School, Scotland
•
• A great puzzle. Wee jamie thought it was easy. The rest of the class all agreed eventually.
• Mrs Gocht, Dremy School
•
• 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
•
• 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
•
• 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
•
• One of my class was very smart and worked it out some others still looked puzzled.
• Year 8, Welshpool High School
•
• Jake was the only one to get it right. Everyone else said £2!
• Primary 7, Mosspark Primary Glasgow
•
• We found this confusing.
• Nick G, Ireland
•
• 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
•
• We also had one smart student who got it!
The class thought it was tricky!
• News.com.au, Australia
•
• Clive, Southampton
•
• 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
•
• 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.

Previous Day | This starter is for 22 January | Next Day

 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?

Christmas Present Ideas

It is often very difficult choosing Christmas presents for family and friends but so here are some seasonal, mathematics-related gifts chosen and recommended by Transum Mathematics.

## Equate board game

Here's a great board game that will give any family with school-aged kids hours of worthwhile fun. Christmas is a time for board games but this one will still be useful at any time of year. Games can be adapted to suit many levels of Mathematical ability.

For Maths tutors working with just one or small groups of pupils this game has proved to be an excellent activity for a tutorial. Deciding on the best moves can spark pertinent discussions about mathematical concepts.

Equate looks a bit like Scrabble--for aspiring mathematicians, that is. Designed by a real mathematician, it works like this: You put down tiles on a board and make points by correctly completing simple equations. Your nine tiles include both numbers and mathematical symbols; you can add on to previous plays both vertically and horizontally. more...

## How Not To Be Wrong

The maths we learn in school can seem like an abstract set of rules, laid down by the ancients and not to be questioned. In fact, Jordan Ellenberg shows us, maths touches on everything we do, and a little mathematical knowledge reveals the hidden structures that lie beneath the world's messy and chaotic surface. In How Not to be Wrong, Ellenberg explores the mathematician's method of analyzing life, from the everyday to the cosmic, showing us which numbers to defend, which ones to ignore, and when to change the equation entirely. Along the way, he explains calculus in a single page, describes Gödel's theorem using only one-syllable words, and reveals how early you actually need to get to the airport.

What more could the inquisitive adult want for Christmas? This book makes a cosy, interesting read in front of the fire on those cold winter evenings. more...

## Graphic Display Calculator

This handheld device and companion software are designed to generate opportunities for classroom exploration and to promote greater understanding of core concepts in the mathematics and science classroom. TI-Nspire technology has been developed through sound classroom research which shows that "linked multiple representation are crucial in development of conceptual understanding and it is feasible only through use of a technology such as TI-Nspire, which provides simultaneous, dynamically linked representations of graphs, equations, data, and verbal explanations, such that a change in one representation is immediately reflected in the others.

For the young people in your life it is a great investment. Bought as a Christmas present but useful for many years to come as the young person turns into an A-level candidate then works their way through university. more...

## Apple iPad Pro

The analytics show that more and more people are accessing Transum Mathematics via an iPad as it is so portable and responsive. The iPad has so many other uses in addition to solving Transum's puzzles and challenges and it would make an excellent gift for anyone.

The redesigned Retina display is as stunning to look at as it is to touch. It all comes with iOS, the world's most advanced mobile operating system. iPad Pro. Everything you want modern computing to be. more...

Before giving an iPad as a Christmas gift you could add a link to iPad Maths to the home screen.

## Aristotle's Number Puzzle

It’s a bit of a tradition to give puzzles as Christmas Gifts to nieces and nephews. This puzzle is ideal for the keen puzzle solver who would like a challenge that will continue over the festive period (at least!).

This number puzzle involves nineteen numbers arranged into a hexagon. The goal of the puzzle is to rearrange the numbers so each of the fifteen rows add up to 38. It comes in a wooden style with an antique, aged look.

Keep the Maths in Christmaths with this reasonably priced stocking filler. more...

## The Story Of Maths [DVD]

The films in this ambitious series offer clear, accessible explanations of important mathematical ideas but are also packed with engaging anecdotes, fascinating biographical details, and pivotal episodes in the lives of the great mathematicians. Engaging, enlightening and entertaining, the series gives viewers new and often surprising insights into the central importance of mathematics, establishing this discipline to be one of humanity s greatest cultural achievements. This DVD contains all four programmes from the BBC series.

Marcus du Sautoy's wonderful programmes make a perfect Christmas gift more...

## Christmas Maths

This book provides a wealth of fun activities with a Christmas theme. Each photocopiable worksheet is matched to the Numeracy Strategy and compatible with the Scottish 5-14 Guidelines. This series is designed for busy teachers in the late Autumn term who are desperate for materials that are relevant and interesting and that can be completed with minimun supervision.

All the activities are suitable for use by class teachers, supply teachers, SEN teachers and classroom assistants and cover topics such as 'How many partridges did the true love give all together?' and 'Filling a sleigh with presents by rolling a dice!'. Children will have lots of fun working through the Christmas Maths themes but also gain valuable skills along the way.

A great source of ideas and another reasonably priced stocking filler. more...

## A Compendium Of Mathematical Methods

How many different methods do you know to solve simultaneous equations? To multiply decimals? To find the nth term of a sequence?

A Compendium of Mathematical Methods brings together over one hundred different approaches from classrooms all over the world, giving curious mathematicians the opportunity to explore fascinating methods that they've never before encountered.

If you teach mathematics to any age group in any country, you are guaranteed to learn lots of new things from this delightful book. It will deepen your subject knowledge and enhance your teaching, whatever your existing level of expertise. It will inspire you to explore new approaches with your pupils and provide valuable guidance on explanations and misconceptions. more...

## Math with Bad Drawings

I had been tutoring the wonderful Betsy for five years. When the day came for our last ever session together before the end of her Year 13, I received this beautiful book as a gift of appreciation.

This a very readable book by Ben Orlin. I'm really enjoying the humour in the writing and the drawings are great.

Ben Orlin answers maths' three big questions: Why do I need to learn this? When am I ever going to use it? Why is it so hard? The answers come in various forms-cartoons, drawings, jokes, and the stories and insights of an empathetic teacher who believes that mathematics should belong to everyone. more...

Click the images above to see all the details of these gift ideas and to buy them online.

## Maths T-Shirts

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