Question

Shinya went to the salon. The cost of her haircut was $16.00. He tipped the barber 15%. What was the total cost of the haircut?

Answer 1

`$18.40`

Shown you a very useful trick to working some numbers out.

Explanation:

`color(blue)("Preamble")`

The symbol % is a bit like units of measurement. Just that in this case it is worth `1/100` of something.

So `15%" "->" "15xx%" "->" "15xx1/100" "->" "15/100`
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`color(blue)("Answering the question")`

15% of $16.00 is written as:

`15/100xx$16.00`

I will show you a trick for doing this without a calculator.
Some numbers are harder but this set will work fine.

15 is the same as 10 + 5
To multiply by 10 is quite straight forward and 5 is `1/2` of 10

`10xx$16=$160`
Now halve it `ul($color(white)(1)80) larr" add"`
`color(white)(aaaaaaaaaa)$240 larr$240 larr" this is "15xx$160`

So `15/100xx$16" "=" "($240)/100`

Divide by the $240 by 100

The tip is `$2.40`

Cost plus tip `->$16.00+$2.40" "=" "$18.40`

Answer 2

`$18.40`

Explanation:

You can calculate this by adding `15%` to `100%` first.

`100% +15% = 115%`

`100%` of `16` means the full price of the haircut.

Finding `115%` of `16` will give you the haircut plus the tip in one step:

`115/100 xx 16 = $18.40`