Monday, July 27, 2009

Can some one help me with this math homework!!!! its 8th grade and im only in 7th?

Given any random, 3-digit number, what is the probability that a number will be:





A) a multiple of 5





B) divisible by 2





C) a square number

Can some one help me with this math homework!!!! its 8th grade and im only in 7th?
A) 179/899


B) 449/899
Reply:well, I hope nobody just gives you the answers because you are smart enough to get these





first, we are only talking about numbers 001 to 999


or do we exclude all the numbers less than 100?


so not including 1000, how many numbers are divisible by 5, in other words what divided by 5 would give you the correct answer?


Second, all even numbers are divisible by 2, so how many even numbers is that?


Third, square numbers can be tricky. What are sqare numbers? the product of a number multipluied by itself, such as 4x4 is 16, 8x 8 is 64, 16 and 64 are both square numbers


Which square is the biggest but less than 999?


you could proceed like this: 10x10 =100, 11x11= 121, 12x12 =144 or start from the biggest square number you know is less than 1000 like 900, 30 x30 = 900, so its at least 30 square numbers (minus the squares less than 100, what is that? 8? 9?)


okay?


BTW Ruth is WRONG!


I just reread the question, if these are probablities, then they should all be written as a ratio, right?
Reply:Sorry, won't solve it for you, but I will give hints.





A probability can be written as the ratio of desired outcomes over possible outcomes. So if you're looking for any of 3 choices out of a total of 12 choices, the probability is 3 out of 12 = 3/12 = 1/4.





In this question, the choices is any 3-digit number, which is all of the numbers from 100 to 999 (900 numbers because 999 - 100 = 899, but you add one more since both 999 and 100 are valid).





For A), find all the numbers between 100 and 999 (inclusive) that are divisible by 5 (i.e., ends in 0 or 5) and divide by 900.





For B), find all the numbers between 100 and 999 (inclusive) that are divisible by 2 (ends in 0, 2, 4, 6, or 8) and divide by 900.





For C), find all numbers that are squares. 100 is a square (10^2).
Reply:a.111.b. 222 c. 121. Not too sure if this is what you want.
Reply:Well basically you just have to think


a) how many numbers that are multiples of 5's are there between 100 and 999 (don't forget to include the 100)





b) how many numbers that are multiples of 2's are there between 100 and 999 (don't forget to include the 100)





c. How many squares between 100 and 999 (dont' forget to include the 100)





Then whatever answer you get, the probabilty will be that number out of 899

curse of the golden flower

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