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### Course: 7th grade (Illustrative Mathematics)>Unit 6

Lesson 6: Lesson 11: Using equations to solve problems

# Two-step equation word problem: computers

Learn how to construct and solve a basic linear equation to solve a word problem. Created by Sal Khan.

## Want to join the conversation?

• Hi!

Why do we round the number ''370.3'' to ''371''?

While I do understand that 0.3 isn't a whole computer - and that Sal wants to determine the minimum number of computers Marcia needs to sell in order to make a profit -, I don't get why we should round numbers up.

The reason I ask is because, a few minutes ago, I made an exercise that told me that 22.25 months should be rounded to 23 months! Isn't the decimal too low to make the digit to the left of the decimal point go up?

Sorry if I wasn't able to explain myself better. Thanks in advance!

Pedro Carvalho

PS: The problem that told me to round 22.25 up to 23 is from Khan Academy. It is from the Linear Equation Word Problems.
• There's a difference between rounding a number to the nearest integer (in which case 370.3 would become 370 and 22.25 would become 22) and rounding up a number, which we do when we want to know the smallest integer that solves a problem. Here, 370.3 would be the smallest number of computers that would allow Marcia to make a profit. But she cannot sell 0.3 computers, so we need to find the smallest integer that solves the problem. 370 won't do, because it is smaller than the smallest number that allows a profit -- so selling 370 won't make a profit. So we need to round UP to the next integer higher, which is the smallest integer that solves the problem.
• How is \$0 a profit? Profit is defined as a "financial gain"- google dictionary. So, how is zero a gain? I understand that at the end of the video the final answer was 371, but his original intention was to find out the amount of computers she needs to sell to make zero dollars.
• It makes sense to first find the number of computers that need to be sold in order to break even (no gain and no loss), so that we can then find the minimum number of computers that need to be sold to make a profit.

Money is gained per computer sold. So any number of computers sold that is more than the number needed to break even does make a financial gain. Note that in the end, the number of computers that need to be sold to break even is a decimal. When this is rounded up to the next integer, this integer number of computers sold does result in a financial gain.
• am i the only one that never watches these videos?
• yes. you are.
• Would it be wrong if I just used division?
E.g. 10,000 / 27 ?
• That is what Sal eventually got to doing. While that answers the question, Marie may want to ask different profit questions, breaking even will not make a business viable. Plus, this does not sound like a very good business to be in.
• How do you get 0 as the profit because I thought it should be a positive or a negative
• Profit = Earnings - expenses.
As such, profit can be negative (a loss); positive (you actually made money); or 0 you earned nothing.
If you earn enough money to cover your expenses but no extra, then you have 0 profit.
• can't this just be a simple division question, 10000 divided by 27?
• Yes which is what he ends up doing, but there is also value in trying to translate word problems into Math symbols because it may not always be that simple
• tested to see if i could get it right before i watched the formula
10,000 / 27 = 370.3 (370 = x)
370 x 27 = 9990 (not >10,000)
370 + 1 = 371
371 x 27 = 10,017 (>10,000)
x = 371
same answer with much less steps
• What is really frustrating is that you can just do this problem by dividing 10,000 divided by 27, and you get your answer. Why isn't the problem something you can only answer using this method?