# Think of a Number

## Ten students think of a number then perform various operations on that number. You have to find what the original numbers were.

##### Level 1Level 2Level 3DescriptionHelpAlgebra

This is level 1: Whole number THOAN problems. You can earn a trophy if you get at least 7 questions correct.

 $$\times 2$$$$+3$$$$37$$Seth says:'I think of a number. I double my number and add 3 the answer is 37'What number was Seth first thinking of? Working: Antonio says:'I am also thinking of a number. If I multiply my number by 2 and add 2 the answer is 40'What number was Antonio first thinking of? Working: Richard says:'I think of a number. I multiply my number by 3 and add 3 the answer is 54'What number was Richard first thinking of? Working: Miquel says:'Can you guess what number I am thinking of if when I multiply it by 2 and add 2 the answer is 32?'What number was Miquel first thinking of? Working: Colin says:'If I divide my number by 5 and add 6 the answer is 22'What number was Colin first thinking of? Working: Cody says:'If I multiply my number by 3 then add 2 then add 3 then add 2 the answer is 40'What number was Cody first thinking of? Working: Alejandro says:'I am thinking of my favourite number. If I add 12 to my number then divide the result by 2, the answer is 13'What number was Alejandro first thinking of? Working: Caden says:'My plan was to add 4 to my number then multiply the result by 3. Then I multiplied the result by 4 and finally subtracted 5. The answer is 79'What number was Caden first thinking of? Working: Blake says:'I decided to add 4 to my number then multiply the result by 3, After that I subtracted 5 then doubled the result. The answer is 68'What number was Blake first thinking of? Working: Carson says:'If I multiply my number by 6 and subtract 6 then multiply the result by 6, the answer is 3 less than 399'What number was Carson first thinking of? Working:
Check

This is Think of a Number level 1. You can also try:
Level 2 Level 3

## Instructions

Try your best to answer the questions above. Type your answers into the boxes provided leaving no spaces. As you work through the exercise regularly click the "check" button. If you have any wrong answers, do your best to do corrections but if there is anything you don't understand, please ask your teacher for help.

When you have got all of the questions correct you may want to print out this page and paste it into your exercise book. If you keep your work in an ePortfolio you could take a screen shot of your answers and paste that into your Maths file.

## Transum.org

This web site contains over a thousand free mathematical activities for teachers and pupils. Click here to go to the main page which links to all of the resources available.

Please contact me if you have any suggestions or questions.

## More Activities:

Mathematicians are not the people who find Maths easy; they are the people who enjoy how mystifying, puzzling and hard it is. Are you a mathematician?

Comment recorded on the 12 July 'Starter of the Day' page by Miss J Key, Farlingaye High School, Suffolk:

"Thanks very much for this one. We developed it into a whole lesson and I borrowed some hats from the drama department to add to the fun!"

Comment recorded on the 2 May 'Starter of the Day' page by Angela Lowry, :

"I think these are great! So useful and handy, the children love them.
Could we have some on angles too please?"

Teacher! Are you delivering Maths lessons online?

Tutors! Are your tutorials now taking place via a video link?

Parents! Has home-schooling been thrust upon you at short notice?

There are many resources to help you on the Maths At Home page. From ready made lesson plans to software suggestions and it's all free.

Stay safe and wash yout hands!

#### Bidmaze

Find your way through the maze encountering mathematical operations in the correct order to achieve the given total. This is an addictive challenge that begins easy but develops into quite a difficult puzzle.

There are answers to this exercise but they are available in this space to teachers, tutors and parents who have logged in to their Transum subscription on this computer.

A Transum subscription unlocks the answers to the online exercises, quizzes and puzzles. It also provides the teacher with access to quality external links on each of the Transum Topic pages and the facility to add to the collection themselves.

Subscribers can manage class lists, lesson plans and assessment data in the Class Admin application and have access to reports of the Transum Trophies earned by class members.

If you would like to enjoy ad-free access to the thousands of Transum resources, receive our monthly newsletter, unlock the printable worksheets and see our Maths Lesson Finishers then sign up for a subscription now:

Subscribe

## Go Maths

Learning and understanding Mathematics, at every level, requires learner engagement. Mathematics is not a spectator sport. Sometimes traditional teaching fails to actively involve students. One way to address the problem is through the use of interactive activities and this web site provides many of those. The Go Maths page is an alphabetical list of free activities designed for students in Secondary/High school.

## Maths Map

Are you looking for something specific? An exercise to supplement the topic you are studying at school at the moment perhaps. Navigate using our Maths Map to find exercises, puzzles and Maths lesson starters grouped by topic.

## Teachers

If you found this activity useful don't forget to record it in your scheme of work or learning management system. The short URL, ready to be copied and pasted, is as follows:

Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for those learning Mathematics anywhere in the world. Click here to enter your comments.

For Students:

For All:

## Description of Levels

Close

Level 1 - Whole number THOAN problems

Level 2 - Decimal THOAN problems

Level 3 - Negative decimal THOAN problems

Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.

## Example

Daniel says 'If I double my number and add 6 the answer is 30'

### Method 1 - Work backwards

Start at the end of the sentence with the answer 30 and undo all of the operations Daniel performed on his number in reverse order.

30 minus 6 then divide by two

The number Daniel was thinking about was 12

### Method 2 - Form and solve an equation

Let the number that Daniel is first thinking of be n.

2n + 6 = 30

Subtract 6 from both sides

2n = 24

Divide both sides by 2

n = 12

The number Daniel was thinking about was 12

Don't wait until you have finished the exercise before you click on the 'Check' button. Click it often as you work through the questions to see if you are answering them correctly. You can double-click the 'Check' button to make it float at the bottom of your screen.

Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.

Close