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### Course: Pre-algebra > Unit 3

Lesson 1: Intro to ratios# Basic ratios

In this video, the instructor explains ratios using three examples: amusement park ride lines, Katie's book collection, and a picture of apples and bananas. Ratios compare two quantities and can be written as "a to b" or "a:b." The video demonstrates how to find and interpret ratios in various situations.

## Want to join the conversation?

- In real life I never used ratios, so my question is are ratios very useful?(30 votes)
- In real life I never used ratios, so my question is are ratios very useful?(32 votes)
- Ratios are very usefull in cooking.

For example, for every 2 cups of flours I need 1 cup of sugar. 2:1 ratio of flour to sugar.(45 votes)

- Do u have videos like this in Spanish my school does math in Spanish and the vocabulary is different making it a lot harder ?(20 votes)
- You can turn on Spanish subtitles.(28 votes)

- what does it really mean when Sal says for every blank there is blank(10 votes)
- it is just different way of say for example 3 to 4 so you could also do 3:4 or for every 3 there is 4. So it i just a different way to specify the problem. there are 3 different ways you can say or write it.(4 votes)

- Can a rate be converted into a ratio, and vice versa?(7 votes)
- Yeah, you can convert ratios into rates and back, although going back is less useful. It is called unit rates. Unit rates, which are a ratio in which the denominator's unit is one, allow us to compare. To calculate unit rates, we simply divide the two numbers in the fraction. The resulting decimal form is the unit rate. Unit prices are a special type of unit rate comparing an item's cost per unit, such as dollars and cents.(7 votes)

- Did you know that you can plot ratios on a coordinate plane? I find that quite interesting!(8 votes)
- I tried to simplify the first question be couldn't.(5 votes)
- The ratio is 11 : 4, since the numbers share no common factors, there is nothing to simplify.(3 votes)

- Are all these examples right?(5 votes)
- Hey ya'll.

I need your help.

Here is the problem:

At a party, the ratio of the number of cheese sandwiches to the number of ham sandwiches is 4:7. The ratio of tuna sandwiches to the number of ham sandwiches is 3:2. What is the ratio of the number of tuna sandwiches to the number of ham sandwiches to the number of cheese sandwiches?

The way I solved it:

T : H : C

7 : 4

3 : 2

But 7 isn't divisible by 2. At least evenly. And you can't have a decimal in a ratio. Should I mark this a typo? Or NEI (Not Enough Info)? Can anyone help me with this please?(4 votes)- round the decimal down to the base number (the number before the point).(2 votes)

- can ratios go higher than two numbers like can I have a ratio that's like 7 diffrent things(3 votes)
- Yes, ratios can go up to as many things as you want.(4 votes)

## Video transcript

- [Instructor] Let's do
some example questions dealing with ratios. So we're told, "The table shows
the number of people waiting "in line for different
rides at an amusement park." So 15 people are waiting in
line for the roller coaster, four people for the slingshot, 12 people waiting in line
for the bumper cards, and 11 people in line for the round-up. "What is the ratio of
people waiting in line "for the round-up "to the people waiting in
line for the slingshot?" Pause this video and see
if you can figure it out. So we wanna know the ratio
of the people waiting in line for the round-up, this is
the round-up right over here, to the number of people waiting
in line for the slingshot. So, there's 11 people waiting
in line for the round-up, and there are four people waiting
in line for the slingshot, so the ratio is 11 to four. Or for every 11 people
in line for the round-up, there are four people waiting
in line for the slingshot. Let's do another example. "Katie loves to read! "In the last few months, she
has read three graphic novels, "two mysteries, four
science fiction novels, "and 21 comic books. "What is the ratio of sci-fi
novels to comic books?" So once again, pause this video and try to work it out on your own. All right, so we wanted to know
the ratio of sci-fi novels, so she has four sci-fi novels, the ratio of that to comic books. She has 21 comic books. So the ratio is for
every four sci-fi novels, she has 21 comic books. Do you want me to do
that in that other color? She has 21 comic books. So the ratio is four to 21, the ratio of sci-fi novels to comic books. Four sci-fi novels for
every 21 comic books. Let's do one more example. This is strangely fun. "What is the ratio of apples to bananas?" Pause this video and try to figure it out. So let's see, there are
one, two, three apples. So for every three apples,
how many bananas are there? Well, there's one, two,
three, four bananas. So the ratio of apples to, the ratio of apples to
bananas is three apples for every four bananas. Order matters. If they said the ratio
of bananas to apples, then this would be four to three, but they say apples to
bananas, three to four. Three apples for every four bananas.