Think of a Number

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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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\( \times 2\) \(+6\) \(36\) Hunter says: 'I think of a number. I double my number and add 6 the answer is 36' What number was Hunter first thinking of?	Working:
Jayden says: 'I am also thinking of a number. If I multiply my number by 2 and add 3 the answer is 35' What number was Jayden first thinking of?	Working:
Juan says: 'I think of a number. I multiply my number by 3 and add 2 the answer is 44' What number was Juan first thinking of?	Working:
Charles says: 'Can you guess what number I am thinking of if when I multiply it by 2 and add 3 the answer is 9?' What number was Charles first thinking of?	Working:
Aaron says: 'If I divide my number by 5 and add 5 the answer is 23' What number was Aaron first thinking of?	Working:
Lucas says: 'If I multiply my number by 3 then add 3 then add 6 then add 6 the answer is 60' What number was Lucas first thinking of?	Working:
Luis says: 'I am thinking of my favourite number. If I add 8 to my number then divide the result by 2, the answer is 14' What number was Luis first thinking of?	Working:
Owen says: 'My plan was to add 5 to my number then multiply the result by 4. Then I multiplied the result by 3 and finally subtracted 4. The answer is 152' What number was Owen first thinking of?	Working:
Landon says: 'I decided to add 3 to my number then multiply the result by 3, After that I subtracted 6 then doubled the result. The answer is 102' What number was Landon first thinking of?	Working:
Diego says: 'If I multiply my number by 4 and subtract 6 then multiply the result by 2, the answer is 6 less than 74' What number was Diego 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

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ChrisMaths

Answers

Go Maths

Maths Map

Teachers

Description of Levels

Curriculum Reference

Example

Method 1 - Work backwards

Method 2 - Form and solve an equation