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Lesson 2: Fractions in contexts

# Fractions in contexts

Sal uses fractions to represent real-world contexts.

## Want to join the conversation?

• Can you multiply fractions?
• Yes you can multiply fractions.
• how do you divide fractions
• Good question! There are at least two methods.

1) Invert the second fraction (the fraction you are dividing by) and then multiply the fractions.

2) Replace the fractions with equivalent fractions that use the same denominator. Then divide the new numerators and cancel out the denominators.

Note: an advantage of using two methods to solve a math problem is that you can use the second method to check your answer.

Example: let’s do 2/3 divided by 3/4.

Method 1):
2/3 divided by 3/4
= 2/3 x 4/3
= (2x4)/(3x3)
= 8/9.

Method 2):
2/3 divided by 3/4
= 8/12 divided by 9/12
= 8 divided by 9
= 8/9.

Have a good day!
(1 vote)
• Are fraction unsolved division problems?
• Yea, that could make sense, but try keeping in mind that fractions are still numbers just like 1, 2 and 3.

Try imagining fractions as simplified division, because sometimes we don't need to know the exact value and sometimes we can't write out the whole value, like in the equation: 1 ÷ 3 answer is something along the lines of 0,3333333 and so on. So to simplify such numbers we use fractions like 1/3th.
• can you multiply fracion
• Yes, you can add, subtract, multiply, and divide any fractions (except for division by zero).

To multiply fractions, multiply numerators together, and multiply denominators together.

A shortcut called cancellation can be used, if any numerator and any denominator have a common factor other than just 1. In this shortcut, first divide the numerator and denominator by the common factor (almost like reducing fractions). Then multiply numerators and multiply denominators.

Example: let’s do 3/5 x 10/11.

Without shortcut:
3/5 x 10/11 = (3x10)/(5x11) = 30/55 = 6/11.

With shortcut: the numerator 10 and denominator 5 have a common factor of 5. So divide them each by 5. So 10 changes to 2, and 5 changes to 1, but the answer stays the same.

3/5 x 10/11 = 3/1 x 2/11 = (3x2)/(1x11) = 6/11.

Caution: using this cancellation shortcut for a numerator and denominator belonging to different fractions only works for multiplication! So for example, we cannot say that 3/5 + 10/11 = 3/1 + 2/11. Clearly 3/5 + 10/11 is less than 2, while 3/1 + 2/11 is greater than 3.

Have a good day!
• can you divide fractions?
• yes you can
• Hepful,understandable but could use more time on the diver one.
• What does Sal mean by one eighth?
• one eighth or 1/8 is like one slice of a pizza cut into 8 slices, hope that helps :)
• why does sal use divers?🤷