If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Arithmetic>Unit 10

Lesson 6: Multiplying fractions and whole numbers

# Multiplying fractions and whole numbers visually

Learn the concept of multiplying fractions and whole numbers. Watch how to visually represent this process and practice understanding the relationship between fractions and whole numbers in multiplication. Created by Sal Khan.

## Want to join the conversation?

• I'm just wanting to confirm and understand why:
2/5 = 2 x 1/5
and why isn't it like before with mixed numerals where this is done:

2 x 1/5 = ((2 x 5)+1)/5 = 11/5 ?

is there a conceptual difference i am missing? thanks in advance !! :)
• Yes there's a conceptual difference.

I believe you are confusing multiplication of a whole number and a fraction, with addition of a whole number and a fraction. Many students have difficulty in math, including higher levels such as algebra, ultimately because they confuse the fundamental concepts of addition and multiplication.

((2 x 5)+1)/5 is equivalent to the mixed number 2 and 1/5. This mixed number means 2 + 1/5, not 2 x 1/5.

2 x 1/5 can be thought of as the repeated addition 1/5 + 1/5, which is clearly 2/5.
• Im bored don't uo vote me
• me to ican
• Sal explained it in a simple way, but it is confusing for me. I am here to know whether to do reciprocal in the multiplication of fractions. Can someone pls clarify my question?
• You do not have to use reciprocals when multiplying fractions, only when dividing.
• *why can't we just add it the normal way.like 1/5+3/4=4/9*
• You cant just add the denominators as well as adding the numerators, you need to find a common factor.
• How do you multiply by 1000000
• Any time you're multiplying by a number that is a 1 followed by some number of 0's, you can simply add on that amount of 0's. If I were to multiply 37 by 10, my answer would be 370. Multiplying 42 by 100 results in 4200. Multiplying 13 by 1 million (1000000) results in 13 million (13000000)
• Do they ever answer us back?cause i asked them something from like 3 years ago
• People DO answer your questions, but there are thousands of questions, so it's certainly possible that not every one gets an answer.

Many of the people answering these questions are those who have taken the course and have mastered all of the concepts - in other words former students who are volunteering their time to answer questions.
• did you know that if a 10 kg cube on a surface with no friction bumps into a 1 kg cube against a wall then it bounces three times (in total of it bouncing against the wall and the cube) if a 100 kg cube bounces into it (still with the same conditions) then it bounces 31 times, and if its a 100 kg cube it bounce's 314 and if you kept timesing the bigger cube by ten it will always be the digits of pie
• If whatever happens to the denominator happens to the numerator why is the whole number only multiplied by the numerator and not the denominator? Are whole numbers +-x/ fractions only between the whole number and numerator?