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First you want to find the circumference of the drive by using the circumference formula:

2*pi*r = 2 * pi * .06 = 0.38 meters

This will be the distance the speck of dust travels in one rotation.

Now multiply that number by the number of rotations occuring in one minute (9400).

9400 * .38 = 3544 meters/minute

That number represents the distance the speck of dust travels in one minute. Now you can divide that number by the number of seconds in a minute to get the speed in m/s.

3544/60 = 59 m/s

I used rounded numbers so that the page wasn't cluttered, so be sure to use unrounded numbers until the end so you get an accurate answer.

A CD-ROM drive in a computer spins the 12-cm-diameter disks at 9400 rpm .

1. What would be the speed of a speck of dust on the outside edge of this disk?

9400rpm / 60sec  = 470/3 revs per second

In one revolution, the particle would travel 2pi(12/2)  = 12 pi  cm

So...the velocity  = [ 470/3 ] * [ 12 pi] cm  = 1880pi cm / sec

76.4705882352941176

Just multiply the numerators of both fractions and the denominators of both fractions to get:

650/8.5

I'm assuming you can't use a calculator so multiply both the numerator and denominator by 10 to get rid of the decimal in the denominator ----> 6500/85

You can reduce this fraction by dividing both the numerator and denominator by 5 to get your final answer of 1300/17

Its obviously 19

1. What is its frequency in rev/s?

[33 + 1/3] / 60   =  [100/3] / 60  = 100/180 =   5/9  revs per second

2. What is its period, in seconds?

If it spins at 5/9 revs per second, then it takes 9/5 sec to make a full rotation....and this is the period

Cphill: Is it any easier or simpler to find x from x^2+1/x^2=62, which comes to: 4 + sqrt(15), then add its reciprocal to it which gives you=8. No?.

I'm not sure what you mean by this, but I think you are talking about rounding.

If you need to round a decimal like 7.235 to the first decimal place, then you just look at the number after the first decimal place (3). If that number is less than 5 then you keep the first decimal place the same, but if that number is greater than or equal to 5 then you increase the first decimal place by 1 digit.

So in this case, the number after the first decimal place (the hundredths place) is  3 so that means you round down.

Therefore, the number rounded to the tenths (first) place is 7.2

If the number was 7.259 then the rounded answer would be 7.3

12,13,15,18,20

The median is the number right in the middle, i.e., 15

Not all products (or quotients) of the invertible functions will have inverses

Examples:

f(x) = 1/x

f(x)  = 1/x^2

Both of these have inverses

Product of the original functions =  1/x^3    this is one-to-one  so it has an inverse function

Quotient of the original functions  = either  x  or 1/x.......both of these are one-to-one  so both have inverse functions

However consider :

f(x)  = x - 3

f(x) = x + 5

Both of these functions are one-to-one and thus have inverses

However........their product =  x^2 + 2x - 15......and this is not a one-to-one function, so it will have no inverse [ unless we restrict the domain]

You need to find the least common multiple to find out how often they have band on the same day. So in other words, what is the smallest number that is divisible by both 5 and 6.

You can check the multiples of each number and find the first one that is in common, but eventually you will be able to recall very quickly what the LCM is of two common numbers.

In this case, Bob and Jill have band together every 30 days.

Just google it!!.

The square root of 49 is 7.

It may be helpful to memorize all of the perfect squares up to 15 or so.

This site has perfect squares listed up to 999 (not as if you need to know that many): http://www.mathwarehouse.com/arithmetic/numbers/list-of-perfect-squares.php

12

I'm assuming that what you mean is you're trying to convert a decimal like 0.234238923978230523 to a percent.

To do this, you just move the decimal point to the right twice, and you'll end up with 23.4238923978230523 %

You know what math is if you can type!!!!!!! 

Thank you sooooooooooo much!!! You are so nice!!  :)

I'm assuming you mean something like 2.3/4.5

I would recommend converting the decimals to fractions ----> 23/10 ÷ 45/10

Now you can take the reciprocal of the bottom fraction and multiply it by the top ----> 23/10 * 10/45 = 230/450

230/450 can then be reduced to 23/45.

He is an Italian mathematician! Born in 1170 in Pisa Italy!

When a fraction is in the denominator, just simply take the reciprocal of the fraction and multiply it by the numerator.

8 * (6/5) = 48/5 

If you think about it, dividing is just another way to multiply. For example, 1/2 is equal to 1 mulitplied by the reciprocal of 2. So in the case of dividing two fractions, take the reciprocal of the fraction in the denominator and multiply it by the fraction in the numerator.

So (1/2) ÷ (3/5) is also equal to (1/2) * (5/3)

So now you just multiply the numbers in the numerator and the numbers in the denominator to get your answer:

(1*5)÷(2*3) = 5/6 

Great

I didn't have time to work this out before....let me do so now.....

x + y = 8       (1)

u - v = 6        (2)

x + u   = 13    (3)

y + v = 8        (4)

Multiply (3) by -1 and add to (1)  →   y - u = -5   (5)

Add (2)  and (4)  →   y + u =  14    (6)

Add (5)  and (6)    →   2y = 9  →    y = 9/2

Using (6), u = 14 - 9/2  =  19/2

Using (1),  x = 8 - 9/2 = 7/2

Using (4). v = 8 - 9/2  = 7/2

Use a front slash /

examle:4/5