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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.

\( \times 2\)

\(+6\)

\(44\)


Jordan says:
'I think of a number. I double my number and add 6 the answer is 44'
What number was Jordan first thinking of?

Working:

Correct Wrong


Gavin says:
'I am also thinking of a number. If I multiply my number by 2 and add 2 the answer is 6'
What number was Gavin first thinking of?

Working:

Correct Wrong
Conner says:
'I think of a number. I multiply my number by 3 and add 5 the answer is 44'
What number was Conner first thinking of?

Working:

Correct Wrong
Aiden says:
'Can you guess what number I am thinking of if when I multiply it by 5 and add 5 the answer is 75?'
What number was Aiden first thinking of?

Working:

Correct Wrong
Isaac says:
'If I divide my number by 5 and add 5 the answer is 16'
What number was Isaac first thinking of?

Working:

Correct Wrong
Jason says:
'If I multiply my number by 2 then add 2 then add 5 then add 2 the answer is 33'
What number was Jason first thinking of?

Working:

Correct Wrong
Cameron says:
'I am thinking of my favourite number. If I add 8 to my number then divide the result by 2, the answer is 23'
What number was Cameron first thinking of?

Working:

Correct Wrong
Hunter says:
'My plan was to add 4 to my number then multiply the result by 6. Then I multiplied the result by 2 and finally subtracted 6. The answer is 234'
What number was Hunter first thinking of?

Working:

Correct Wrong
Jayden says:
'I decided to add 5 to my number then multiply the result by 3, After that I subtracted 4 then doubled the result. The answer is 148'
What number was Jayden first thinking of?

Working:

Correct Wrong
Juan says:
'If I multiply my number by 2 and subtract 3 then multiply the result by 5, the answer is 2 less than 137'
What number was Juan 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 24 May 'Starter of the Day' page by Ruth Seward, Hagley Park Sports College:

"Find the starters wonderful; students enjoy them and often want to use the idea generated by the starter in other parts of the lesson. Keep up the good work"

Comment recorded on the 25 June 'Starter of the Day' page by Inger.kisby@herts and essex.herts.sch.uk, :

"We all love your starters. It is so good to have such a collection. We use them for all age groups and abilities. Have particularly enjoyed KIM's game, as we have not used that for Mathematics before. Keep up the good work and thank you very much
Best wishes from Inger Kisby"

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Featured Activity

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An online darts game for one or two players requiring skill, strategy and mental arithmetic. It provides an enjoyable way to practise adding and subtracting two and three digit numbers.

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Teachers

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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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