 1825 Views 50 Replies 14 Participants Last post by  Vicster
Right, My eldest (9) yr 5 key stage 2 has come home with this homework,now the way i am working it out seems rather tricky for her, yet can't see how it is done any other way of it being done unless I'm missing a really obvious way.

Heres what she has been given (I don't have ascanner so i'll type it as one the sheet)

Use the multiplication facts given to work out the answer to the questions. Remember to show your working. The first one has been done for you.

2 x 8 =16 3 x 8 =24 what is 5 x 8? 16+24=40

Now that is the example

4 x 7 = 28..................what is 8 x 7?
3 x 8 = 24................. what is 9 x 8?

Now this is the way we did the first two

4 x 7 = 28 4 x 7 =28 what is 8 x 7? 28 + 28 = 56
3 x 8 = 24 6 x 8 = 48 what is 9 x 8? 24 + 48 = 72

now we have done it like this..

We subtract the first number ie 4 (x7) from the 8(x7) to get the next sun that goes in between.

it works for pretty much all the sums, some need subractions though, she is doing partitions at the moment.

any one else confused??

Am I being thick & not seeing a simple way round it & I'm making it more difficult?

See less See more
1 - 20 of 51 Posts
thats the only way I see of doing it!
Now thats what I thought until

10 x 6 = 60...............what is 9 x 6?

which can be done but its a subtraction.
looks right to me, i think, dont remember doing that when i was a school :crazy: oh, and Ive got a degree in applied computing so algebra and numbers are my kinda thing!
Thankyou, I thought I was going nuts & making harder then it should have been as the boy next door in her class did it a completey different way :crazy:
What's the point of that???

Is it supposed to help abstract thought or something?
Nige G said:
What's the point of that???

Is it supposed to help abstract thought or something?
I think the point is for them to work out different ways of getting to the same result possibly? is called making children use their brains.
Vicster said:
Now thats what I thought until

10 x 6 = 60...............what is 9 x 6?

which can be done but its a subtraction.
10 x 6 = 60 -1 x 6 = -6 What is 9 x 6? 60 + -6 = 54
its application maths or something like that.

Its to make children use known knowledge to gain results they may not think they are able to work out.

hence they may know or be able to work out 4x but not 8.

But by using the applied knowledge they know 8 is 2 x 4 hence they can apply the same to either end of the equation and get the desired result.

The later ones are extension activities whereby they can use their newly gained confidence and simply subtract a single figure from a known figure especially factors of ten.

for a child to work out something x9 is difficult but they know the 10x easily as its simply a case of adding a zero.
if they therefore know the result of 10x they know 9 times is one unit less and cn therefore easily work it ou.

hope this helps See less See more
Nige G said:
10 x 6 = 60 -1 x 6 = -6 What is 9 x 6? 60 + -6 = 54
Thats the way i did that one to.

4 x 6 =24...........what is 6 x 8?
Nige G said:
10 x 6 = 60 -1 x 6 = -6 What is 9 x 6? 60 + -6 = 54
you have overcomplicated this by bringing in negative figures.

in this case it would be a known figure of 10 x 6 which is simply a 6 with a 0 added on giving 60

now asked for 9 x 6

we know what 10 is and 9 is one less than ten

we know the factor is 6 in this case so 1 x 6 is 6 which we take away from the know figure of 60

giving us 54 DOH
Vicster said:
Thats the way i did that one to.

4 x 6 =24...........what is 6 x 8?
this one is exactly the same as first examples

only thing being the numbers have been transposed so first and last figures are the common factors.

at first seems like 4 and 6 and and 8 which is difficult

but if you realise that you can write these numbers either way round it becomes simple

This turns into

4 x 6 =24 what is 8 x 6

now it becomes clear you simply have to times result by two to get 48
See less See more
Nic B-C said:
you have overcomplicated this by bringing in negative figures.

in this case it would be a known figure of 10 x 6 which is simply a 6 with a 0 added on giving 60

now asked for 9 x 6

we know what 10 is and 9 is one less than ten

we know the factor is 6 in this case so 1 x 6 is 6 which we take away from the know figure of 60

giving us 56
we know non of this and it is hurting our heads :incheek: Nic B-C said:
you have overcomplicated this by bringing in negative figures.

in this case it would be a known figure of 10 x 6 which is simply a 6 with a 0 added on giving 60

now asked for 9 x 6

we know what 10 is and 9 is one less than ten

we know the factor is 6 in this case so 1 x 6 is 6 which we take away from the know figure of 60

giving us 56
54.

60 minus 6 = 54.  Icky said:
54.

60 minus 6 = 54.  :lol:
I really dont know why i put 56 there!!!!

anyway principal was right
From the example

2 x 8 =16 3 x 8 =24 what is 5 x 8? 16+24=40

The multiplier is 8 so it would appear that the multiplier stays the same.

eg:

3 x 5 = 15 ................... what is 12 x 5?

60 - 15 = 45 45 / 5 = 9 so.........

3 x 5 = 15 9 x 5 = 45 what is 12 x 5? 15 + 45 = 60
See less See more
Nige G said:
From the example

2 x 8 =16 3 x 8 =24 what is 5 x 8? 16+24=40

The multiplier is 8 so it would appear that the multiplier stays the same.

eg:

3 x 5 = 15 ................... what is 12 x 5?

60 - 15 = 45 45 / 5 = 9 so.........

3 x 5 = 15 9 x 5 = 45 what is 12 x 5? 15 + 45 = 60
This is how we have done it, the multipler has stayed the same. we have got the correct answer whether it was adding or subtraction.
Its about x the answer by the amount you have at front

if you have say 4 and need 8 you need to x the result by the same factor of the front number
1 - 20 of 51 Posts