Here are two of their solutions:įor this challenge task, I figured out that the rule given worked for any number that I tried. Shreya, Sirat, Lelia, Divya, Kirsten, Reetinderit, Ryan, Harman, Shazana and Agam from ”‹Glendenning Public School in Australia also worked on this task. This is Anh Minh's work:Įlifsu from International School Laren in Holland made some 'think of a number' machines in a fully animated powerpoint presentation. Whatever number is chosen, the answer will always be 5.Īnh Minh from British Vietnamese International School Hanoi, Steven from Reading School in the UK and Qianwei from Humanitree in Mexico showed how this works using algebra. The next step subtracts the random number, leaving you with 5. You can see that even though the number goes through a lot of equations, you still end up with (random number + 5). While the instructions are performed, the answer from the second last step is (random number + 5). If you look at the blue line and orange dots that are next to the instructions that the interactivity gives, the blue line (a random number) and the orange dots (the units that the interactive tells a person to add) are separate, even though when the instructions are used, it is one number that a person sees. The idea is that, if (this is an example) 3 was added at the start to another random number, the number and 3 seem to be added together, but by subtracting the other number at the end, the answer will always be 3. When you enter a number and follow all the instructions, you always get 5 at the end.
#A number minus 11 is 3 plus#
Your original number - Your original number + 5 = 0 + 5 = 5.įergus from Golspie High School in Scotland explained this idea very simply:Īt the end you subtract the original number so if you ignore the original it makes it :ģ, $\times$ 2 = 6, plus 4 = 10 then halved is 5 And since whenever you subtract a number from itself, you always get 0.įor example, if we use 99 as the original number, we will still end up with: This is always true whatever number you chose at the beginning because at the end, you're subtracting your original number from your original number. Your original number - Your original number + 5 (which is obviously, 5!) In this case, 50.įinally, when you subtract the original number, you will have: Then you halve your number, and you will have your original number plus 5. Then you add 4, and now you have twice the original number plus 10. When you double it, you have twice your original number plus 6. When you add 3, you have your original number plus 3. Shao from The Australian International School in Malaysia”¨ wrote:
This proves that you can do it in any order. Also we worked out that doing the calculations backwards and using the opposite symbol also gives you five. This works because when doing the calculation you are working out the opposite and the middle part in the calculation always equals five. Leo, Mikki, Jodi, Amy, Cienna, Jedd, Charlie, Freya, Orla, Freya, Merry, Spike and Mo from Reepham Primary School worked on this task.
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