Y5 and Y6 Brainteaser
Think of a Number
Try this challenge:
Follow this sequence of steps.
Think of a number between one and ten.
Double your number.
Add ten.
Halve your number.
Take away the number you first thought of.
Your answer should be five.
Why is the answer always five?
Does this work if you start with a larger number?
Can you make a series of similar questions for which the answer is always eight?
Post your findings on the Blog, or bring them to me in school.
3 comments:
To mrs.Davies
The reason the answer is always 5 is because that when you double the number,it becomes an even number and when you add 10 and when it gets halved it has a greater chance of being,say if your number was 8,a number like 13,so when you subtract 8,the number becomes 5,which is the same as all numbers from 1 to 10.
Noah
Hi Mrs.D!!!Had a go at the brain teaser and i really don't get how the answer is always 5.Could you please explain it to me in school.
Mahrooshay
Hi Mrs Davies
it will always be 5 even if you start with a bigger number.
Daniel.c
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