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### Course: Algebra (all content)>Unit 3

Lesson 14: Linear models word problems

# Linear models word problem: book

Sal solves a word problem about a person reading a book, The solution involves the modeling of the situation as a linear function.

## Want to join the conversation?

• why didn't you dived the the amount of pages the book have with page it take him one hour to read?
• I'm working my way from basic arithmetic up through vector calculus as a thorough review of my middle school, high school, and college math. Now that I'm in the Algebra section, I've notice that the word problems have gone full metric leaving the US standard units out. I miss the US units. They are so elegant, beautiful, warm and familiar. Will I ever see them again in any of the Khan Academy videos and problems? As a prospective high school teacher, I might actually browse the 'Common Core' modules. I sure hope to find some US units there. I'd hate to think they're not expected to be taught in the future when much of our industry uses this system of weights and measures. Thanks! -John in Seattle
• Sometimes, they do use "US" units(called English units), however for the most part they use metric. Mostly only the united states, Liberia, and Burma us English units of measurements. Due to the internationality of this website, they mostly use metric. Metric units are also the units most commonly used for science and engineering. Besides all that metric is easier to use and convert than the English system.
• I was taking one of these tests about linear equations after watching the videos, I am still so confused. Like how does 3x=7y or something like that seem right when you put it down on the grid but its wrong and its like on the other side and is at 8y, 11x?
• How can one decide which is the Y equivalent and which is the X equivalent on the "y=mx+b" general formula?
• The x is the independent, and the y is the dependent variable. Which depends on the other. So if every minute you gain 6 pounds, the x is the time in minutes and the y is the pounds.Hope this helps.
• I just don't get how to solve my problem. I watched the math video about it but I'm not understanding.
• what if there were more than ten hours.... like 40 hours.... is there an easier and faster way to get the answer than constantly subtracting or adding 55.
• i understand the first part of the lesson but once he talks about how to find how long it took the person to read the book I just completely got confused. HELP!
(1 vote)
• First you have to understand that at 4 hours, Naoya has 330 pages left to read. He also reads at a constant rate of 55 pages an hour. So, as every hour passes by, the number of pages will decrease by 55. A quicker way to do this than just subtracting 55 from each new number that represents pages left, you can just divide 330 by 55. This gets you to 6. You also have to realize we didn't start at 550, the total number of pages in the book, so we have to add 6 hours to the number of hours it took to get to 330 pages left, which is 4 hours. An added 6 hours + 4 hours that Naoya was reading gets you to 10 hours. Dividing 550 (total # of pages) by 55 (constant rate of pages per hour) will also get you the total number of hours needed to read the book. Hope you found this useful.
• How do I watch a video I have already watched? It doesn't seem to be allowing me.