Arithmetic and pre-algebra Ratios, proportions, units and rates Rates Usain Bolt's Average Speed Finding Unit Rates Finding Unit Prices Rate problems 0.5 Rate problems 1 Rate problems 2 Finding Unit Rates Finding Unit Rates Back Finding Unit Rates ⇐ Use this menu to view and help create subtitles for this video in many different languages. You'll probably want to hide YouTube's captions if using these subtitles. Jayda takes 3 hours to deliver 189 newspapers on her paper route. What is the rate per hour at which she delivers the newspaper? So this first sentence tells us that she delivers, or she takes, 3 hours to deliver 189 newspapers. So you have 3 hours for every 189 newspapers. That's what the first sentence told us. But we want to figure out the rate per hour, or the newspapers per hour, so we can really just flip this rate right here. So if we were to just flip it, we would have 189 newspapers for every 3 hours, which is really the same information. We're just flipping what's in the numerator and what's in the denominator. Now we want to write it in as simple as possible form, and let's see if this top number is divisible by 3. 1 plus 8 is 9, plus 9 is 18. So that is divisible by 3. So let's divide this numerator and this denominator by 3 to simplify things. So if you divide 189 by 3. Let's do it over on the side right here. 3 goes into 189. 3 goes into 18 six times. 6 times 3 is 18. Subtract. Bring down the 9. 18 minus 18 was nothing. 3 goes into 9 exactly three times. 3 times 3 is 9, no remainder. So if you divide 189 by 3, you get 63, and if you divide 3 by 3, you're going to get 1. You have to divide both the numerator and the denominator by the same number. So now we have 63 newspapers for every 1 hour. Or we could write this as 63 over 1 newspapers per hour. Or we could write this as 63, because 63 over 1 is the same thing as 63 newspapers per hour. Questions Tips & Feedback Be specific, and indicate a time in the video: At 5:31, how is the moon large enough to block the sun? Isn't the sun way larger? Have something that's not a question about this content? Post a tip or feedback General discussion about the site Report a technical problem with the site Request a video or feature This discussion area is not meant for answering homework questions. Formatting tips Cancel or ( total) Share a tip When naming a variable, it is okay to use most letters, but some are reserved, like 'e', which represents the value 2.7831... Suggest a fix At 2:33, Sal says "double bonds" but should say "single bonds." Have something that's not a tip or feedback about this content? Ask a question General discussion about the site Report a technical problem with the site Request a video or feature This discussion area is not meant for answering homework questions. Formatting tips Cancel or Discuss the site For general discussions about Khan Academy, visit our Reddit discussion page. Flag inappropriate posts Here are posts to avoid making. If you do encounter them, flag them for attention from our Guardians. abuse disrespectful or offensive an advertisement not helpful low quality not about the video topic soliciting votes or seeking badges a homework question a duplicate answer repeatedly making the same post wrong category a tip or feedback in Questions a question in Tips & Feedback an answer that should be its own question about the site a question about Khan Academy (Visit our FAQ) a post about badges a technical problem with the site (Report a problem) a request for videos or features
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