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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 1 Level 2 Level 3 Description Help Algebra

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

\( \times 2\)

\(+2\)

\(8\)


Vanessa says:
'I think of a number. I double my number and add 2 the answer is 8'
What number was Vanessa first thinking of?

Working:

Correct Wrong


Amanda says:
'I am also thinking of a number. If I multiply my number by 2 and add 4 the answer is 18'
What number was Amanda first thinking of?

Working:

Correct Wrong
Ariana says:
'I think of a number. I multiply my number by 3 and add 6 the answer is 66'
What number was Ariana first thinking of?

Working:

Correct Wrong
Rebecca says:
'Can you guess what number I am thinking of if when I multiply it by 3 and add 4 the answer is 22?'
What number was Rebecca first thinking of?

Working:

Correct Wrong
Caroline says:
'If I divide my number by 5 and add 2 the answer is 5'
What number was Caroline first thinking of?

Working:

Correct Wrong
Amelia says:
'If I multiply my number by 5 then add 4 then add 2 then add 4 the answer is 50'
What number was Amelia first thinking of?

Working:

Correct Wrong
Mariah says:
'I am thinking of my favourite number. If I add 10 to my number then divide the result by 2, the answer is 23'
What number was Mariah first thinking of?

Working:

Correct Wrong
Jordan says:
'My plan was to add 6 to my number then multiply the result by 2. Then I multiplied the result by 3 and finally subtracted 3. The answer is 45'
What number was Jordan first thinking of?

Working:

Correct Wrong
Jocelyn says:
'I decided to add 5 to my number then multiply the result by 3, After that I subtracted 2 then doubled the result. The answer is 56'
What number was Jocelyn first thinking of?

Working:

Correct Wrong
Arianna says:
'If I multiply my number by 3 and subtract 6 then multiply the result by 3, the answer is 4 less than 40'
What number was Arianna first thinking of?

Working:

Correct Wrong
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.

Why am I learning this?

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 23 September 'Starter of the Day' page by Judy, Chatsmore CHS:

"This triangle starter is excellent. I have used it with all of my ks3 and ks4 classes and they are all totally focused when counting the triangles."

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!"

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Practice Papers

Practice Papers

Mathematics GCSE(9-1) Higher style questions and worked solutions presented as twenty short, free, practice papers to print out.

Answers

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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:

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Description of Levels

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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.

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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.

Log in Sign up

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