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### Course: 7th grade (Illustrative Mathematics) > Unit 5

Lesson 14: Lesson 14: Solving problems with rational numbers# Rational number word problem: cab

Budgeting money is one of the most valuable math skills you'll learn. Practice with us as we figure out how much money is left after a cab fare. Created by Sal Khan.

## Want to join the conversation?

- I did this a completely different way. I personally found this video a tad confusing, however I understand there are multiple ways of doing math.

What I did was 5 miles X $2.50 = 12.5 (now you got the only number you don't know)

Next I just did this: $20 - $2.50 (cab fee) - $12.5 - $1 (tip) = $4(12 votes) - Why are there 7 videos in a row? does anyone else have it like this with 7 videos in a row?(14 votes)
- ikr! 7vids and 1 test! =((1 vote)

- could it also be done like this?

$20-$2.50 = $17.50

$17.50 - ( $2.50x5)

= $5 - $1

=$4(5 votes)- There are many ways in solving a problem. What you just did is one way, and Sal 's is another way. In conclusion both ways are correct if you end up with the same answer!(4 votes)

- guys I just noticed sal is secretly using a calculator!(6 votes)
- I got this question: to take the taxi, it costs $3.00 plus an additional $2.00 per mile traveled. you spent exactly $20 on a taxi, which includes a $1 tip left.

then it asks me how much miles I have left

I am soo confused(4 votes)- well, you know the 3 and 1 dollar won't change, so you can take those out, leaving you with 16 dollars, and it is probably asking how many miles you can travel with that money(3 votes)

- Why are there so many videos on just one topic? i think i get it my the second or third video.(2 votes)
- Michael just finished a great meal in a restaurant in Wisconsin. The sales tax in Wisconsin is 5% and it is customary to leave a tip of 15% for the waiter. The tip amount is calculated on the price of the meal before the tax is applied. Sales tax is not calculated on tips.

If Michael left $18 on the table to cover his meal, tax, and tip, what was the price of his meal before tax and tip?

"Adding 20 percent to an amount is the same as multiplying that amount by 1.20" ---This hint threw me off, I have no idea how to get the decimal 1.20, and it doesn't really tell you why or how. Also, I got it wrong because I did something like this 18 - (18*0.2) = 14.4. The rest of the hints explain it well but that one point I'm not getting.(2 votes)- let's call P the price of the meal before tax and tip.

Together, the tip and tax are 20% but it's important to remember that the tip and tax are calculated on the**price before tax and tip**(P). $18 is the price**after**tip and tax. Using your method this would be expressed as`P + (P*0.2)=18`

P + 0.2P =18

1.2P = 18

can you see what the hint is trying to tell you?(1 vote)

- plz help. I don't understand any of theese, and they are non-relevant to the lesson(1 vote)
- Sandy has 20 dollars.

Here's one way we can do it.

Sandy enters the cab. Now she has $17.50 ($20-$2.50)

Sandy goes 5 miles. Now she has $5 ($17.50-($2.50 times 5))

Sandy gives a 1 dollar tip. Now she has $4 ($5-$4)

Sandy has $4.

Here's another way to do it.

Sandy enters the cab.

Sandy goes 5 miles.

Sandy gives a $1 tip.

$2.50+($2.50x5)+$1=$16

$20-$16=$4

Sandy has $4.

All we're doing is subtracting how much Sandy pays from how much she starts with.(2 votes)

- what is going on here(1 vote)
- i think this is easy but sometimes the rounding is hard for me. i just don't like the rounding at all😐(1 vote)

## Video transcript

Sandy is taking a
cab in New York City. The taxi fare includes a base
charge of $2.50 as soon as you enter the cab, plus an
additional $2.50 per mile traveled. If Sandy starts off
with a $20 bill, takes the cab for five
miles, and leaves a $1 tip, how much money will
she be left with? Well let's first just think
about how much this five mile cab ride is going to cost her. So cab-- I'll call
it the cab fare. So it's going to be $2.50 just
when you get into the cab, plus $2.50 per mile. Well she's going
to go for 5 miles-- let me write it this way--
times $2.50 per miles. So the cab fare here is just
going to be $2.50, this $2.50, plus 5 times $2.50. Let's see, 5 times
$2.50, that is $12.50. So this is plus $12.50. $2.50 plus $12.50
is going to be $15. So just the cab fare
is going to be $15. And then Sandy gives a $1 tip. So fare plus tip is going
to be equal to the cab fare $15 plus $1 which
is equal to $16. So then answering the
question, how much money would she be left
with with a $20 bill? Well we could
write her change is going to be, she's going
to give a $20 bill, the fare plus tip
is $16, minus $16. So she's going to have
$4 left in change.