Tomorrow is one of our favourite lessons in Class 5 – Maths problem solving!
For those of you who want go get into the logical thinking required for this lesson before tomorrow, try this puzzler:
Think of a number
Add 3 to it
Double your answer
Take 6 away from the answer
Halve your number
What do you notice?
Does this always work? Explain your reasons…
There will be a special prize for some fantastic reasoning. Remember to try lots of different numbers. Please blog your working like you would do in a Maths lesson.
You have until Monday 30rd September to enter your responses. Best of luck guys!
6+3=9
9×2=18
18-6=12
12-6=6
Well I started with 6 and when I finished the whole thing i came back with the number I started with.
2
2+3=5
2×5=10
10-6=4
4 divided by 2=2
in this way you get back to the number you started with but with zero you don’t.
0
0+3=3
3+3=6
6-6=0
but you can’t halve zero.
Actually I’ve worked it out and half of zero is zero!
I love your blogs Mr Mastrelli
Yes.
When I add 3 and times 2 it makes 6, then minus 6 makes 0.
I just times my number by 2 and then divided by 2.
1+3=4 4+4=8 8-6=2 2-1=1
2+3=5 5+5=10 10-6=4 4-2=2
3+3=6 6+6=12 12-6=6 6-3=3
4+3=7 7+7=14 14-6=8 8-4=4
5+3=8 8+8=16 16-6=10 10-5=5
I think I’ve worked this out. I love problem solving! I hope you keep putting these problems on here!
Mrs Hearson
Start of with your original number. Now add 3 and double your number. When you double your number you do not only
double your original number but double 3 too. Now you have twice your original number plus 6.Take away that 6.
Now you have your original number times 2.Halve your number.End with your original number.
You always end up with the same number because your basicly doing the oposite to what you’ve already done but in a different order for example:
24+3=27
27+27=54
54-6=48
1/248=24
so it’s always the same number you had.
I tryed…12
12+3=15
15+15=30
30-6=24
Half of 24 is 12
My reasons are…you come back to the number you started with!!
I also tryed…6
6+3=9
9+9=18
18-6=12
half of 12 is 6
you see?
What got you onto maths so much Mr Mastrelli?
number 16
16+3=19
double 19=38
38-6=32
half 32=16
Yes!
Because two threes make six for example. Double the number, minus six and half of it is the first number you started.
I started with 7 and ended up with 7
You always end up with the number you started with
eg. I chose the number 5
5 + 3 = 8
8 x 2 = 16
16 – 6 = 10
10 ÷ 2 = 5
you are always add 6 to your number then double the number have now then take away 6 and halve the number
My number was 12
12 + 3 = 15
15 x 2 = 30
30 – 6 = 24
24 / 2 = 12
Well done Sophia and Ella, our winners for this blog. Hope you enjoy the pens!
Thanks Mr Mastrelli! I have been using my pens alot this weekend! They are great.
2+3=5 5+5=10 10-6=4 10-10=0
Yes it does work with all the numbers,and I think it is something to do with the fact that you double the 3 which gives you six then you take six away (you are taking away the same number as you are adding). You also double the number then halve it – giving the same number as you had before
(example 12 + 3 (=15) x2 (= 30) – 6 (=24) halve it =12