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## Pre-algebra

### Unit 11: Lesson 7

Arithmetic with numbers in scientific notation

# Simplifying in scientific notation challenge

Sal simplifies a very hairy expression in scientific notation.  Created by Sal Khan.

## Want to join the conversation?

• At about the sec mark, Khan talks about the product of dividing:

9.2 * 10^5
11.5 * 10^2

I worked the equation before Khan. Instead of dividing 9.2 by 11.5 * 10^2, I said divide by
1.15 * 10^3 (.) We came up with the same answer; 8 * 10^2.

My doing scientific math problems that way (changing any multiplication involved in the numerator or denominator to correct scientific notation, will that cause me any problems down the road (?))
• Don't worry. If you know more than one way, it can really pay off. For example, say you take an important exam, and you come across a difficult question on this topic. You can solve one way, and if you think it's wrong, you can confirm it the other way.
• At shouldn't he have converted 11.5 to scientific notation first for consistency's sake?
• Yes he could have. I believe he did not do that for the sake of working with easier numbers.
• This is a kind if out there question but what kinds if things would you use scientific notation for?
• Science things, for example the population of the world or the size of a cell
• @ ish isn't it 0.08 because Sal multiply both numbers by ten
• Sal didn't mulply by 10. He has 0.8 as the leading number in his answer. The leading number has to be in the range 1 to 9 inclusive to be in correct scientific notation. So, Sal changes 0.8 into scientific form: 0.8 = 8 * 10^(-1). Then, he multiplies the 10's together by adding their exponents to get his final answer of 8 * 10^2.

Hope this helps.
• May someone please explain this to me I was understanding it at first but now it's a blur scientific notion is not easy for me to understand...
• How would we use these or real life problems?? (Engineering specifically)
• Is his name Khan
• At the mark, Khan talks about simplifying things into si=cientific notation. But how do you simplify something that is irrational into scientific notation? something like π?
(1 vote)
• π has a meaning unto itself just like √2, √3, e, or other irrational numbers, so leaving them in an answer does not require scientific notation. If you are solving a real world problem, you have to round irrational numbers off anyway, so the rules of science is that you round to the number of places of the given number with the smallest number of places.