About this video
A movie theater charges $10.50 per ticket and $5 per bucket of popcorn, but you never buy popcorn. Because you only pay for tickets, the total price is proportional to the number of tickets: 1 ticket is $10.50, 2 are $21.00, 3 are $31.50, and price divided by tickets is always 10.50.
You'll be able to
- decide whether a real-world price is proportional to the number of items bought.
- ignore information that doesn't affect the relationship, like the popcorn price.
- write the relationship as price = 10.50 × number of tickets.
Key words
- proportional
- The total changes by the same multiplier as the number of items, so total ÷ items is always the same.
- ratio
- A comparison by division, like price divided by number of tickets.
Transcript
- A movie theater charges $10.50 per ticket and $5 per bucket of popcorn. You never buy the popcorn because you think it's too expensive. Is the total price you pay proportional to the number of tickets you buy? This is interesting, because they tell us the price of a bucket of popcorn, but then they tell us that we never buy the popcorn.
So I guess, I don't know they even told us what the price is; maybe to confuse us. Is the total price you pay proportional to the number of tickets you buy? Well, you're only buying tickets; you're not gonna be buying any popcorn, so yeah, you're gonna spend $10.50 for every ticket, so it should be proportional.
Just to see that a little bit clearer, let's draw a little table here. So, number of tickets; and then price, the total price. We're assuming I never buy the popcorn. So, if I buy one ticket, the price is going to be 10.50. If I buy two tickets, it's gonna be two times 10.50, or $21.00.
If I buy three tickets, gonna be three times 10.50, which is what? 31.50. And so, you can see the ratio between price and number of tickets, it's always going to be 10.50. 10.50 divided by one; 21 divided by two; 31.50 divided by three; it's always going to be 10.50.
That's 'cause the price, put another way, the price is just going to be 10.50 times the number of tickets. So, clearly a proportional relationship.
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