Broken Calculator

A Maths Lesson Starter Of The Day

Using only these keys on your calculator make each of the target numbers on the balloons. Use the least number of key presses possible.






Congratulations. You did it with 0 button presses.
Can you do it using a smaller number of button presses?

You could also try the Flash version which uses a different type of calculator.


Topics: Starter | Arithmetic | Calculator | Place Value | Problem Solving

  • Malcolm P, Dorset
  • A set of real life savers!!
    Keep it up and thank you!
  • Pete Freer, Rotherham
  • Prompted a great deal of enthusiasm and competition to find the quickest way!
  • Joe Murray, Linwood High
  • We did it in 35 moves beat that!
  • Kenny Dyson, Deans Community HS, Livingston
  • We got 34.
  • Russ Skinner, Grant Park High School, Winnipeg, MB, Canada
  • I found an answer for 30 moves
  • George Abbot, Guildford Surrey
  • 27th Sept We did it in 26 goes. Beat that
  • Jamie Pascoe, Notton House School
  • I completed this exercise in 28 moves taken screen shot I can email it to you!! :):)
  • BIS Jakarta, Indonesia
  • My clever class did it in 24 buttons!
    Beat that!
  • Mr. B., Essex, UK
  • Can you please provide how you did it in 26 steps ive been trying forever and cant do it in less than 32
  • Year 8 Set 2 Brinsworth Comp, Rotherham
  • As a class we have managed to complete this in 24 moves!
    Can anyone beat that?
  • Transum,
  • Thanks everyone for their feedback. Perhaps we should set some rules here.
    When you first load this starter the target numbers are 16, 24, 97 and 624. If you refresh the page or click the "Change Numbers" button you will get four random target numbers. Let's agree that we are looking for the least number of button presses which achieves the original four target numbers.
    Rather than just the number of button presses you should also record the buttons pressed E.g. 15+1+5+… etc
  • Peter Freer, Brinsworth Comp Rotherham
  • Here is the solution for 24 moves from my Y8 class, a team effort.

    11 + 5 = CE 11 + 1 + + + + 1 515 + 11 + 1 =
    (16) (24) (97) (624)
  • George Abbot School, Guildford Surrey
  • We have also managed to do it in 24 moves. Start with getting the 24 and get the 16 last by using the clear button
  • Kerry robb, Brinsworth Rotherham
  • Alex Robb's mum class 8b did it in 22 moves feeling quite smug.
  • Mr Barnes, Bradford
  • This was a really good starter, I did it with my top set year 7 and they loved it, especially when they realised there were shorter ways than what they had done, it made them determined to find it.
  • Tom, LGS
  • I'm not great at Maths but I did it in 63.
  • Mr Bracewell, Hanham High, UK
  • Word - my year 10 bottom set (and proud) got a 27 first go. 'ave sum.
  • Mrs Lowry, SPA
  • We are from Park Academy we did it in 24
  • Amber Read, 11 yrs,
  • We had a go at this in class and no one could figure out how to do it in 24 moves... but i tried it at home and got it!!! 24 moves!! YAY!!!
  • L Holmes, Ruislip
  • Bishop Ramsey Year 11 did this in 21 goes. Well done Chris!!!!
  • Dr Mills, 7M1, Stockport Academy
  • We solved it in 35, and we think we could get it down to 33.
  • Tegan Macintosh,
  • This was a fun activity but we couldn't beat 50 moves.
  • Staines, Surrey
  • Thanks for the challenge! My year 12 class found a 7 move solution! Beat that!
  • George Thoroughbad, Ethniklashistan, JK
  • Calculators are the devil's tools. I remember a time when people relied on intelligence, not coordination! I hate sports!
  • Mrs, Cornwall, Claydon High School
  • My Year 7s have found 16 in 5 moves, 24 in 13 moves, 97 in 14 moves and 624 in 15 moves. Do you know what you the lowest amount of moves is for each number?

  • Year 9, George Abbot
  • We managed to do it in 24 moves. Nice and easy. We await the next challenge.
  • Sydney, Richmond
  • I did it in 29 moves BEAT THAT.
  • Mrs Wright, Pen CP
  • We did it in 29 too! Well done Y4 at Pen Cp. Yeah.
  • Mr Smith, Renfrew High School
  • My S4 class managed this in 23 moves with the solution below:
    15 + 1 + + 5 + + 550 = CE
    11 + 1 + + + + 1 =.
  • J. Miley, KSSC, Birmingham
  • Our Year 10's did it in 17-ish!
    ...but we're very proud!
  • Mrs Simpson, Forres Academy
  • Our S1 class who are 11/12 years old did it in 21 moves. They were chuffed!
  • Mrs. Chetwynd-Knagg, Greengate Junior School
  • Our Year 4 class did it in 20 steps, very proud!
  • Charlie, Waddy Lancashire
  • We are in class 6 and we got it in 16.
  • Mrs Fleet, Wanstead High School
  • We are in year 4 and did it in 7 :).
  • Transum,
  • Please note that all of the comments above refer to the Flash version of this activity which uses a different type of calculator.
  • Jack F, Risca
  • Year 8 did it in 48 moves. Hooray.
  • Alex W, Risca
  • Year 9 took 42 moves. Well done to Alex.
  • Shannon And Natasha And Class, Risca
  • We did 40 moves.
  • S Sharples And Year 7, Helston
  • We tried this as a year 7 class and got 44 but will be coming back next lesson as we are sure we can beat it! We loved it.
  • S Sharples Year 10, Helston
  • We got this in 36 moves and would love to know how they got it in 7 because we do not think it is possible.
  • Carmo, Hillsborough Secondary
  • Did it in 41 moves.
  • Carol Lowry, Chapel High School
  • I am disappointed that you can no longer refresh and get the same numbers as classes like to try the same challenge a few times.
    Otherwise great activity.

    [Transum: The Start Again button allows you to do the challenge again with the same numbers]
  • 7A1, Montgomery High School
  • Montgomery High School Blackpool UK Class 7A1 (Mr Gunn's) cracked this in 34 moves. We are awesome!
  • Mr John Smith, Lc32
  • We did it in 15 moves!NOW WHO CAN BEAT THAT!??.
  • Mr Simon Perry, Orley Farm, Harrow
  • My year 4 Maths set managed to work this out in 34 steps - needless to say I was pretty impressed as I gave them the target of 40!
  • Mrs.Wafaa, DAR AL FIKR
  • We did it in 10 steps ..... dun dun dunnn UNBEATABLE !!!

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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