Think of a Number

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.

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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.

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\( \times 2\) \(+21\) \(13\) Gabriella says: 'I think of a number. I double my number and add 21 the answer is 13' What number was Gabriella first thinking of?	Working:
Jenna says: 'I am also thinking of a number. If I multiply my number by 2 and add 9.1 the answer is -6.1' What number was Jenna first thinking of?	Working:
Kimberly says: 'I think of a number. I multiply my number by 3 and add 7.3 the answer is -17.6' What number was Kimberly first thinking of?	Working:
Stephanie says: 'Can you guess what number I am thinking of if when I multiply it by 2.6 and add 8.8 the answer is -2.64?' What number was Stephanie first thinking of?	Working:
Alexa says: 'If I divide my number by 5 and add 4.8 the answer is 4.08' What number was Alexa first thinking of?	Working:
Avery says: 'If I multiply my number by 4.3 then add 9.6 then add 3.4 then add 8 the answer is -7.81' What number was Avery first thinking of?	Working:
Andrea says: 'I am thinking of my favourite number. If I add 19.2 to my number then divide the result by 2, the answer is 5.3' What number was Andrea first thinking of?	Working:
Leah says: 'My plan was to add 2.1 to my number then multiply the result by 4.5. Then I multiplied the result by 2.1 and finally subtracted 5.2. The answer is -64.735' What number was Leah first thinking of?	Working:
Madeline says: 'I decided to add 3.2 to my number then multiply the result by 3, After that I subtracted 3.9 then doubled the result. The answer is -6.6' What number was Madeline first thinking of?	Working:
Nevaeh says: 'If I multiply my number by 4.9 and subtract 8 then multiply the result by 9.9, the answer is 3.1 less than -546.647' What number was Nevaeh first thinking of?	Working:

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.

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Instructions

More Activities:

Featured Activity

Tran Towers

Answers

Go Maths

Maths Map

Teachers

Description of Levels

Curriculum Reference

Example

Method 1 - Work backwards

Method 2 - Form and solve an equation