KS1 / KS2 Maths: What is multiplication?

Voiceover:
In a world without maths,a land where people forgot, who will save the day?(Dave whistles)

Dave:
Oh no, I’ve run out of bricks.Hi Sally… Yeah, that’s right, another brick please…ok, thanks.Thanks Sally.

(Dave whistles)

Oh no.I’ve run out of bricks!Hi Sally…yeah that’s right…how did you know? Ok, thanks.Thanks Sally.

Mrs Sharma:
Cup of tea Dave?

Dave:
Ooo I’d love one.

Dave:
Two sugars please. Oh no no no no no!I’ve run out of bricks!

Mrs Sharma:
How are you getting on?

Dave:Err not bad, yeah, should be done in a couple of years.

Mrs Sharma:
A couple of years? This sounds like a job for…Multiplication Boy!

Narrator:How can Multiplication Boy help Dave to get Mrs Sharma’s wall built faster? Adding one brick at a time is taking forever.Dave needs to know how many bricks it’ll take to build the whole wall in advance.That’s right, he needs to use multiplication.

Multiplication has a special symbol of it’s own, but really it’s just repeated addition. Now let’s have a closer look at that wall.The wall’s made of sections. Each section is 1, 2, 3, 4, 5 bricks high.

Dave has finished one section, but there’s four more to go.

So how many bricks will Dave need to finish the wall?He could ask Sally for five bricks and build a section. Then order another five bricks and build the next section. Another five, and another five.

We can write this down as 5+5+5+5 or 4 lots of 5 or 4 x 5

Dave:
Ok great, I’ll call Sally.

Hi Sally

(offscreen) Sally:
Alright Dave, how’s it going?

Dave:
Yeah good. Can I order…5 bricks?

(offscreen) Sally:
Oh my goodness, 5, are you sure?

Dave:
Oh hang on, err let me just check.Are we sure about this? No? Ah. Err sorry Sally, I’m going to have to call you back.

Narrator:
Dave could order groups of 5 bricks at a time, but he’d still need 4 deliveries.Wouldn’t it be better if he ordered all the bricks he needed in one go?

Dave:
Ok cool, so 4 groups of 5 bricks.

Narrator:
Hang on Dave, how many bricks is that?

Dave:
4 lots of 5.

Narrator:
Yes but how many in total?

Dave:
Oh…I don’t know.

Narrator:Multiplication Boy, did you bring your number line?Let’s count it out.

One group of 5, takes us to 5. Next group of 5, takes us to 10, so 2 groups of 5 is ten. Next group takes us to 15, 3 groups of 5 is fifteen. One more group takes us to 20. 4 groups of 5 is twenty. We can write this out as4 x 5 = 20So Dave will need 20 bricks to finish the wall.

Dave:
Hi Sally, huh, you’re not going to believe this…I need 20 bricks.

(offscreen) Sally:
20 bricks! You’re having a laugh. Are you sure?

Dave:
Yup! 20 bricks please Sally.

(offscreen) Sally:
Wow, you’ll probably get the whole job done with that lot.

Dave:
That’s the plan.

Narrator:
Great.Well done Multiplication Boy. Now Dave has enough bricks to finish the wall in one go.