Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 Re: Exercises » Convert these numbers into other bases » 2013-05-13 00:22:38

Where are you stuck in following the step-by-step directions? wink

#2 Re: Exercises » Continuous velocity exercises » 2013-05-09 23:22:42

julianthemath wrote:

Well, there are many velocity formulas, but let us focus on this formula :

                distance
velocity = -----------
                  time

Let's start.

For a start, what have you tried so far? Where are you stuck?

How many per minute?

julianthemath wrote:

1) Distance = 500 meters and Time = 15 minutes
How many meters per minute?

What did you get when you divided?

julianthemath wrote:

2) Distance = 88 kilometers and Time = 4 minutes and 40 seconds
How many kilometers per minute?

What portion of a minute is forty seconds? What did you get when you divided?

julianthemath wrote:

3) Distance = 17.5 kilometers and Time = 3 minutes
How many kilometers per minute?

Hint: Divide.

julianthemath wrote:

How many per hour?

4) Distance = 117 kilometers and Time = 9 hours
How many kilometers per hour?

Hint: Divide.

julianthemath wrote:

5) Distance = 975 meters and Time = 1 hour and 20 minutes
How many meters per hour?

Hint: Convert the minutes to a decimal portion of an hour. Then divide.

julianthemath wrote:

6) Distance = 400 miles and Time = 1 day
How many miles per hour?

Hint: Convert the day into hours. Then divide. wink

#3 Re: Help Me ! » equation of the line » 2013-05-08 22:12:39

mom wrote:

Find an equation of the line having y-intercept (0,3) and x-intercept (-4,0)

bobbym wrote:

y = ( 3 / 4 ) x + 3

"mom": Do you know how to arrive at the answer you were given? If not, please write back, so you can be helped to learn. Thank you! wink

#4 Re: Help Me ! » equation of a parallel line » 2013-05-08 22:10:34

mom wrote:

Im still lost but thanks Bob

On which part are you lost? Thank you! wink

#5 Re: Help Me ! » help with matrix problem please » 2013-05-06 05:09:36

mrpace wrote:

let M be an invertible matrix. If M^3=M, find the possible vales of the determinant of M.

Since M is invertible, then there exists a matrix M^(-1) such that M*M^(-1) = M^(-1)*M = I.

What happens if you multiply the given equation, either on the left or on the right, by that inverse matrix? What do you know about the value of the determinant of the right-hand side of the resulting equation? wink

#6 Re: Help Me ! » need some help plz » 2013-05-03 05:41:25

aric wrote:

birth weight in US are normally distributed with mean of 340g and a strandard deviation of 45g. If a hospital plans to set up observation condition for the lightest 7% of the babies, what weight is used for the cutoff separating the lightest 7% from the others?

What is the z-score for "7%"?

Plugging this into the equation for computing z-score from the mean, the test value, and the standard deviation, what value do you get for the test value? wink

#7 Re: Help Me ! » Z-Scores » 2013-05-02 00:11:56

ladyrain95 wrote:

I thought I understood the basics of this, but...Anytime I have to find a number from the "Areas Under the Standard Normal Curve" chart I get the wrong number. I don't know what I'm doing wrong.. can someone please help me?

In order to help you figure out what you're doing wrong, you'll need to tell us what you're doing. Please reply with your steps and reasoning. Thank you! wink

#8 Re: Help Me ! » Calculate Aggregate Price Index » 2013-04-23 12:35:46

I'm not allowed to posts links, so try entering this phrase, with the quote-marks, into Google:

"simple aggregate price index"

Then look for a link for an article from the domain "mba-lectures".

Is that the sort of thing you're talking about?

Or are there different rules for "consumption quantities"? (I can't find what those are, actually. It might help if you provided the economics stuff, so we can help you with the math parts.)

#9 Re: Help Me ! » Quantifiers and a predicate » 2013-04-05 00:51:23

FlashBurn wrote:

Statement 2: For all a ∈ A there exists d ∈ D such that H(a, d).

This one I can't figure out. Does it mean that for every a there exists a unique d...or does it mean that d's can be shared by some a's...?

Since Statement 2 doesn't say "there exists a unique d", I would interpret this in the same manner as for Statement 1; namely, that there exists some element d for each a. The element d doesn't have to be unique (a different d for each a). wink

#10 Re: Help Me ! » Stirling's formula » 2013-03-31 23:35:33

For other users, the images contain the following:

...and:

#11 Re: Help Me ! » Non Intersecting chords » 2013-03-31 03:54:12

For other users: The text of the tiny image is as follows:


#12 Re: Exercises » Proof by induction question » 2013-03-18 06:57:34

genericname wrote:

Hi, I am stuck on the last step. What am I supposed to do now?

Problem: Let T(n)=3T(n-1)+2, T(1)=2. Prove by induction that T(n)=3^(n-1)

Here is what I have so far:

Show base case k=1: T(1) = 3^1 - 1 = 2

If T(1) = 2 and if the proposed formula is as you've posted, then T(n) for n = 1 is 3^(1-1) = 3^(0) = 1, not 2. So the base step fails.

You appear, in your work, to have used a different formula from that which was proposed. Is there perhaps a typo somewhere? wink

#13 Re: Help Me ! » Sequencing » 2010-12-21 13:41:00

Mariner wrote:

Hi, I was wondering if I could get your help on some particular number sequence questions and the tricks behind them.

Here are a few.

10, ?, 41, 17, 52, 09
15, ?, 70, 18, 52, 00

Try breaking up the numbers into sets of three digits. Remove the commas and try to find a pattern in:

. . . . .10_, _41, 175, 209

. . . . .15_, _70, 185, 200

There is no real "trick" to this. I just happened to think of it and it just happened to work.

cool

#14 Re: Help Me ! » Finding a percentage of a number » 2010-12-21 13:33:53

Mariner wrote:

...I know for a fact that there are a number of questions that ask for a percentage of a number or quantity of something. I was wondering if I can have some tips on how to do these types of questions in my head or any 'tricks of the trade' if any.

The general equation for is as follows:

. . . . .(this) is (some percent) of (that)

...where "is" means "equals" and "of" means "times".

You'll always be given two pieces of information. Plug those in, and solve for whatever is left, which will be what they're wanting.

cool

#15 Re: Help Me ! » Can Someone Help Me Make Sense of This Algebra Problem? » 2010-12-21 13:30:27

When you get an "answer" that makes no sense, such as "0x = (something other than zero)", then there is "no solution".

When you get an "answer" which is stupid and obviously, such as "1 = 1", then the solution is "all x" or "all real numbers".

cool

Board footer

Powered by FluxBB