Think Back

A Maths Starter Of The Day

Mariah thinks of a number.

She then does the following operations:

Multiply by 2, subtract 2, multiply by 2 then add 52 (in that order).

No calculators allowed

She finds that the number she ends up with is 10 times her original number.

What was Mariah's original number?

Pencil


Topics: Starter | Algebra

  • Teacher, Derbyshire
  • Wednesday, June 24, 2009
  • "Used this as a plenary question to a year 8 lesson on solving equations with x on both sides. Good challenge both in setting up the equation and then solving it."
  • Teacher, Surrey
  • Thursday, January 26, 2012
  • "When checking answer, it only works on non-scientific calculators as they do not apply BIDMAS!!"
  • Mr J, Balshaws
  • Thursday, April 24, 2014
  • "We found this starter very interesting. Harry really loved it!!!"

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This starter has scored a mean of 2.1 out of 5 based on 190 votes.


Previous Day | This starter is for 11 April | Next Day

 

Answers

This question is best answered by forming an algebraic equation then solving it. Let Mariah's original number be x.

First operation gives 2x

Second operation gives 2x- 2

Third operation gives 2(2x- 2)

Fourth operation gives 2(2x- 2) + 52

This is equal to 10 times the original number

2(2x - 2) + 52 = 10x

4x- 4 + 52 = 10x

...

x = 8

Mariah's original number was 8.

Note to teacher: Doing this activity once with a class helps students develop strategies. It is only when they do this activity a second time that they will have the opportunity to practise those strategies. That is when the learning is consolidated. Click the button above to regenerate another version of this starter from random numbers.


Laptops In Lessons

Teacher, do your students have access to computers?
Do they have Laptops in Lessons or iPads?

Whether your students each have a TabletPC, a Surface or a Mac, this activity lends itself to eLearning (Engaged Learning).

Laptops In Lessons

Here is the URL for a concise version of this page without comments or answers.

Transum.org/go/?Start=April11

Here is the URL which will take students to our eQuation Generator which provides unlimited practice solving linear equations.

Transum.org/go/?to=eQuation

 

 




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