Calculating a 10% tip in a restaurant using place value columns

Speaker: I'm just getting ready to go out for dinner with a few friends from work.

I work at a clothes shop in town, which is great, because I get my staff discount.

Maths was never my favourite subject and until last year I used to avoid it, which was making things difficult at work and home.

But I did start this new course in town and then it's given me a much better understanding of how to go about solving a maths problem.

Like tonight, for example, I know that we'll probably have to work out splitting the bill and tips.

Say we decide to leave a tip of 10%.

How do I go about calculating 10% of the total bill?

Usually I would just leave it for someone else to sort out, but actually I know that to find 10% of any amount you just divide by 10.

And we've just been learning new ways of working that out at college.

Tonight I might actually have a go myself at working it out!

Speaker 1: Right, guys, so how do you want to go about sorting this?

Speaker 2: Should we just split it, and add 10% for a tip?

Speaker 1: (TO AUDIENCE) Cool, so now I can use what I learned in college to figure out the percentage.

First I need to figure out what 10% is so I can add it on before we split it.

Well, I know that any percentage can be written as a fraction of 100.

So 100% is the same as 100/100 and 10% is 10/100.

If I divide the top and bottom by 10 I get 1/10, so 10% equals one tenth.

And because it's a tenth, I know I should divide by 10.

(TO OTHER PEOPLE) If you could just bear with me, I just want to try this new trick that I learned at college.

(TO AUDIENCE) If I write this out like this it makes it dead easy for me.

And to divide by 10, I just need to move everything over one column to the right.

(TO OTHER PEOPLE) OK, so the tip is £11.18.

(TO AUDIENCE) Now add that to £111.80 to get the overall total.

Speaker: (TO OTHER PEOPLE) So if we add the £11.18 then that comes to £122.98 - is everyone happy with that?

So £122.98 divided by seven is £17.57, so I suppose it would be easier if we all just rounded it up to £18 each then?

(TO AUDIENCE) I'll just double check that's right. 18 × 7 is £126.