{"id":1478,"date":"2013-12-24t09:00:08","date_gmt":"2013-12-24t09:00:08","guid":{"rendered":"\/\/www.catharsisit.com\/sat\/?p=1478"},"modified":"2015-04-15t20:09:50","modified_gmt":"2015-04-15t20:09:50","slug":"sat-math-probability","status":"publish","type":"post","link":"\/\/www.catharsisit.com\/hs\/act\/sat-math-probability\/","title":{"rendered":"sat math – probability"},"content":{"rendered":"
probability is actually pretty rare on the sat. so don\u2019t freak out about this topic. in fact, i\u2019d only recommend this post for those looking for a near perfect\u2014those who want to make sure they have all their bases covered.<\/p>\n
what you\u2019ll have to know is the following:<\/p>\n
probability (likelihood of something happening) = #of desired outcomes\/# of possible outcomes<\/p>\n
let\u2019s say we want to know what is the probability of rolling \u201csnake eyes\u201d, or two \u20181\u2019\u2019s, on a pair of fair dice. well, how many ways can you roll two \u20181\u2019s? there is only one way. so for a desired outcome\u2014the quantity in the numerator\u2014we are going to write \u20181\u2019.<\/p>\n
now how many different ways can you roll two six-sided dice? (for a review of the fundamental counting principle click here). well, there are six possibilities on each die, so that gives us 6 x 6 = 36.<\/p>\n
therefore, the probability of rolling \u201csnake eyes\u201d with two dice is 1\/36.<\/p>\n
of course things do get a little more complicated with probability\u2014that\u2019s why so many people dread it. below are some medium- to medium-difficult questions for you to sink your teeth into. if you nail all three, the probability of you struggling with a probability question on the test is very low.<\/p>\n
if not, make sure you understand the concepts (see explanations below), and you should do just fine on the probability questions the sat throws at you.<\/p>\n
1. a basket contains a total of 24 balls of yarn. 1\/3 are white, \u00bc are red, 1\/6 are blue, and the rest are black. what is the probability, if you reach into the basket, of pulling out either a red or black yarn?<\/p>\n
2. a six-sided die is thrown three times. what is the probability that on all three rolls a prime number will never come up?<\/p>\n
3. a coin is tossed three times. what is the probability that three \u201ctails\u201d in a row will not show up?<\/p>\n
<\/p>\n
1. hey, a little fun with fractions never hurt! so, if we do the math, we get 8 white, 6 red, and 4 blue. that means the remaining 6 are black. since the question asks for red and black, that gives us 12 (desired outcomes) out of 24 (total outcomes), or \u00bd.<\/p>\n
2. first off, there are three prime numbers on a six-sided die: 2, 3, and 5. what is the probability of not rolling one of these three numbers? 1\/2, since rolling a 1, 4, or 6 would count. now, the probability of rolling an outcome of \u00bd (or 50%) is much like tossing a coin. in this case, we are tossing the coin, or rolling a die with a \u20181\u2019, \u20184\u2019 or \u20186\u2019, three times: \u00bd x \u00bd x \u00bd = 1\/8. answer: (c).<\/p>\n
3. speaking of coins! a quick way of doing this problem is subtracting the probability of getting all tails by the total probability. before we do that a quick thing on the probability space. usually, we talk about something definitely happening as having a probability of 100%. however, 1 also represents a 100%. how? well, if the probability of something happening is \u00bd or 50%, what happens when you multiply both those numbers by 2? you get \u20181\u2019 and 100%. so probability can be defined along a scale from \u20180\u2019 to \u20181\u2019.<\/p>\n
so for the coin toss, \u20181\u2019 represents all possible outcomes. subtracting the probability of all tails from \u20181\u2019 will give us the probability of not getting on tails: 1 \u2013 (1\/2)^3 = 1 \u2013 1\/8 = 7\/8. (e).<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
probability is actually pretty rare on the sat. so don\u2019t freak out about this topic. in fact, i\u2019d only recommend this post for those looking for a near perfect\u2014those who want to make sure they have all their bases covered. what you\u2019ll have to know is the following: probability (likelihood of something happening) = #of […]<\/p>\n","protected":false},"author":10,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[90],"tags":[9,122,60],"ppma_author":[24882],"acf":[],"yoast_head":"\n