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### Course: Grade 7 math (FL B.E.S.T.)>Unit 8

Lesson 1: Basic probability

# Simple probability: yellow marble

In order to find the probability of picking a yellow marble from a bag, we have to first determine the number of possible outcomes, and then how many of them meet our constraints. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• What would be the percentage of the question in the video?
• The answer in a percentage will be 37.5%
• What is the probability of me getting my mommys credit card and spending her entire bank balance on vbucks?!! Also, what is the probability of me getting my dad's credit card and spending all of his money on shiny rocks in gorrilla tag?!
• 0% in getting any and if you manage to there is a 100% chance you will get...
• how do u do probability when it says =
for example p(3 or multiple of 2)?
• When it says p(3 or multiple of 2), it means What is the probability of getting either a 3 or a multiple of 2? To do this, you would add the probability of getting a three to the probability of getting a multiple of 2.
• Do we use rounding for probability?
• Whether we round off our answers (or our intermediate calculations) depends on the problem we're trying the solve, and the conditions we are given. For the kinds of probability calculations we are doing here (that rely mostly on counting procedures) we don't round off, as a general rule.
• I understand this but I need help with this question from DeltaMath "In a popular online role playing game, players can create detailed designs for their characters "costumes" or appearance. Shaniece set up a website where players can buy and sell these costumes online. Information about the number of people who visited the website and number of costumes purchased in a single day is listed below.
97 visitors purchased no costumes
26 visitors purchased exactly one costumes
13 visitors purchased more then one costume
Based on these results, express the probability that the next person will purchase more then one costumes as a percent to the nearest whole number "
• Well, I'm not great at this stuff, but I can at least try.
There are 136 visitors, because 97 + 26 + 13 = 136. 13 visitors purchased more than one costume, so the probability is 13/136. I personally don't understand the last part, so I can't help you there.

Hope this helped! :)
Art3mis
• How does sal draw so good?
• He has a tablet and a stylus that he uses to draw with online, so basically he is just writing with a pen or pencil. No-one could do that with a mouse.
• What is the probability of a 8 sided spinner with 2 red, 3 green and, 3 blue will land on blue as percentage and, decimal?
• Theoretical probability gives 3/8 which is .375 as a decimal or 37.5%.
• How do I do this?