Upside Number

Fonia noticed that her phone number read the same when viewed upside down.

Her number began 081 and was followed by seven digits.


The two digit number formed by the fifth and sixth digits is divisible by eleven.

The two digit number formed by the fourth and fifth digits is divisible by nine.

The two digit number formed by the sixth and seventh digits is a square number.

What is Fonia's phone number?

Updide Number

A Mathematics Lesson Starter Of The Day

Topics: Starter | Number | Puzzles

  • Sue Mainstone, Sir Charles Lucas arts college
  • Should have said todays number was planindromic as well
  • Micky Bullock, Harrogate
  • Another solution is 0816336180.
  • Miss Gilleece, Boldon School
  • My 9A1 got the answer in 3.2 minutes, Chris was the first to come up with the correct answer.......which is quite amazing considering!!!
  • Mrh, Neb
  • I had a student had completed this in less than two minutes! Can anyone beat that!
  • Jay, Yeates
  • Micky, your answer is wrong as it isn't the same when read upside down.
  • Cheryl Joinson, Sychdyn School
  • I'm using starter of the day every mornign in my primary class.
    Our answer was 0811881180 but we have no way of checking if we are correct.
  • Geraint White, Hadleigh High School
  • I got 0819116180.
  • Fran,
  • Another soloution is 0816699180.
  • Cheryl, Sychdyn Primary School
  • Geraint & Fran sorry but both your answers are wrong - the corect answer is at the bottom of this page - and my primary school class got it right! :-).
  • Sally S, Barham School
  • Love reading the comments - sometimes V competitive between teachers themselves;).
  • Mr. Dean, Varee International
  • What about 0810000180?
  • 5DC, Lee On The Solent Junior School
  • We think the answer is 0811881180 :).
  • Top Group Y5, ST JOHN'S SCHOOL
  • The boys loved this.
  • Mr P Darch, FMS - Tom, Luke And Lucy
  • Enjoyed this and my Year 6 class solved in about 4 minutes.
    By the way the only answer is 0811881180 - the others either do not look the same upside down or do not satisfy the other rules.
  • Mr Staples, Otamatea High School
  • My students enjoyed this and some found it quite easy Two boys completed in 2 minutes.
  • Year 8D, Gresham's Prep School
  • We did this as a team
    Forgot to time ourselves - will challenge you all next week!

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.
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Laptops In Lessons

Teacher, do your students have access to computers such as tablets, iPads or Laptops?  This page was really designed for projection on a whiteboard but if you really want the students to have access to it here is a concise URL for a version of this page without the comments:

However it would be better to assign one of the student interactive activities below.

Laptops In Lessons

Student Activity


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