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-0.1

The number of positive integers less than 5000 that are divisible by neither 3 nor 7.

Number  of integers divisible by 3  =   1666

Number of integers divisble by 7  =  714

Number of integers divisible by 3 and 7  =  5000/21    =  238  (Double Counting... )

So.....The number of positive integers less than 5000 that are divisible by neither 3 nor 7 =

4999 - 1666 - 714  + 238   =  2857

You didn't. I can do it in 10 sec XD now that's a bit exaggerated 

1e5 x 90,000,000,000,000

= 1e5 x 9e13

= 9e18

= 9,000,000,000,000,000,000.

2y + 8 = 12

2y + 8 - 8 = 12 - 8

2y = 4

2y /2 = 4 /2

y = 2

This is the Asian way that I learn.

Below is the Western way :)

2y + 8 = 12

2y = 4

y = 2

No wonder why you guys do stuff faster.

You guys should feel thankful that you don't need to do it the Asian way.

Nothing is ONLY for you. You live yourself, do your tasks, and die, peacefully.

Wrong. The figure cannot be constructed.

If the side opposite to 90 deg is 90, then the side opposite to 30 deg should be \(90\sin 30 = 90\times \dfrac{1}{2}=45\) and should not be 57

If A∩B={b, d}, there should be b and d in set B and should not have a, f, and g.

Also:

You can also report problems to any of the moderators and admins(Melody, CPhill(Chris), Alan, radix, admin). I think radix is not an active moderator though......

Thanks Melody

I assume I have 100g of the drug sample.

74.27% carbon is 74.27 g of carbon

7.79% hydrogen is 7.79g of hydrogen

etc.

Then calculate the amount in moles

74.27g of carbon = 6.184 mol

7.79g of hydrogen = 7.728 mol

12.99g of nitrogen = 0.927 mol

4.95g of oxygen = 0.309 mol

Multiply them by 1000 to become whole numbers

6184 units of carbon

7728 units of hydrogen

927 units of nitrogen

309 units of oxygen

The 4 have no common factors......

So the empirical formula is C₆₁₈₄H₇₇₂₈N₉₂₇O₃₀₉ ????

Not sure about that..... the number seems huge.

I do feel bad after I answer stuff wrong too..but there's really no need to!

It's really easy to miss a detail like that 

The forum have a pretty nice private messaging system and it's pretty easy to use.

Did you not bring your occipital lobe? 

5 x 5 = 25 :)

You can:

1) Use a multiplication table :D

2) Use a calculator :)

\(x = \dfrac{-b \pm \sqrt{b^2-4ac} }{ 2a}\) :D

90 x 9

= 810 :)

Guest #1 is correct.

But I did the wrong stuff I hate myself so much :(

Divide 23 1/2 by 4.

\(23\dfrac{1}{2}\div 4\\ =\dfrac{47}{2}\div 4\\ =\dfrac{47}{2}\times \dfrac{1}{4}\\ =\dfrac{47\times 1}{2\times 4}\\ =\dfrac{47}{8}\\ =5\dfrac{7}{8}\)

Each piece is 5 7/8 inches long :)

Maths is fun MATHS IS AWESOME!! ~MaxWong <-- LOL I really think so XD

Math:

Challenging - definitely

Boring - never!

~ Forum Moderator Melody.

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
~Albert Einstein

Hope you can hate math less than you were :)

Hey your answer isn't even technically wrong 

Wow.

I didn't even think of solving for x and I just thought it was a question to tell you express the perimeter in terms of x.....

I feel so embarrassed now 

500 - 98 + 81 - 71 + 100

= 402 + 81 - 71 + 100

= 483 - 71 + 100

= 412 + 100

= 512

Guest #1 and #2 are both not correct. More patience next time and be more careful!!

The sides of a square are the same length...so

x² + 8x = 5x + 28      Subtract 5x from both sides.

x² + 3x = 28              Subtract 28 from both sides.

x² + 3x - 28 = 0         Factor.

(x + 7)(x - 4) = 0        Set each factor =0

x = -7    or     x = 4

If x = -7, the side length = (-7)² + 8(-7) = -7

But since this is the length of a side, we want a positive number, so x must = 4

If x = 4, the side length = 4² + 8(4) = 48

perimeter = 4 * side length

perimeter = 4 * 48 = 192 units

It is what?

WOOOOOT? XD

\(\dfrac{6}{x-6}+2(x+6)\\ =\dfrac{6}{x-6}+\dfrac{2(x+6)(x-6)}{x-6}\\ =\dfrac{6+2(x^2-36)}{x-6}\\ =\dfrac{2x^2 - 66}{x-6}\\ \)

This is correct, CPhill :D

Perimeter

= 2((x^2 + 8x) + (5x + 28))

= 2(x^2 + 13x + 28)

= 2x^2 + 26x + 56