All Answers

jquan:
Sharon bought a shirt for 25.99, and a skirt for 31.50 and a pair of sandal for 12.98 what would be her total cost after tax if the tax was 8%? (.08)

Add all the amounts up to get the first total

Tax is 8% of first total
8% is 8/100 and of is x so it is just 8/100 x first total

Add the tax to your first total and that is the cost.

MelodyFeb 6, 2014

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tannawirsch:
Okay, so I am having a huge struggle with some Physics questions from Uniform Accelerated Motion.

There are three equations that I can use:

1) V₂ = V₁ + a∆t
2) ∆d = V₁∆t + 1/2 a∆t^2
3) V₂^2 = V₁^2 + 2 a∆d

I am having troubles solving a question using equations (2). Say for example:

A sports car approaches a highway on-ramp at a velocity of 20.0m/s [E]. If the car accelerates ata rate of 3/2m/s^2 [E] for 5.0s, what is the displacement of the car?

The answer is 100m [E] + 40m [E]
∆d = 1.4 x 10^2m [E]

I know that you would add in your variables: ∆d = V₁(20.0m/s) ∆t(5.0s) + 1/2 a(3.2m/s[E]) ∆t(5.0)^2
I know how to get the 100m: (20.0)*(5.0)=100

But how do you get the 40?
Or even how do you get ∆d = 1.4 x 10^2 ?

You were on the right track by formulating ∆d = V₁(20.0m/s) ∆t(5.0s) + 1/2 a(3.2m/s[E]) ∆t(5.0) ²

Yet, what you haven't done is actually filling in the numbers.

This gives ∆d = 20.0*5.0+ (1/2)*3.2 *5.0 ² = 100 + 1.6*5 ² = 100 + 1.6*25 =
100+ 40 =
140 =
1.4* 100 =
1.4 * 10 ²

So, the 20*5 = 100 gives the distance the car travels due to its beginning speed,
and the (1/2)*3.2 *5.0 ² gives the extra distance the car travels due to the extra speed it gains from accelerating.

You calculated the first part by your self but missed the accelerating part.

also 140 = 1.4 * 10 ² which is in essence the same.

The difference is that 140 describes the distance with 3 significant figures while 1.4 * 10 ² describes it with 2 significant figures

If you want to learn more about that look at;

http://www.chem.sc.edu/faculty/morgan/resources/sigfigs/index.html

Reinout

reinout-gFeb 6, 2014

#75

+118741

+6

lostjr126:
easier one (4*2) *5

EASIER ONE
3,5,2,4 and the magic number is 40
(4*2)*5 = 40
Excellent answer lostjr126
------------------------------------------------------------------------------------------------------------------------------------------------------
NEW PUZZES

Here is my version of the magic number (choose the one that is best suited to your ability level)

Rules:
You have to use some or all of the numbers to make the magic number. You are not allowed to use any of the numbers twice. (Unless one was written twice in the first place)
You can use brackets, +, -, x, or divide and that is it.

EASIER ONE
3,2,8,10 and the magic number is 120

HARD ONE (Hopefully it is easier than Reiner-g's last one. I think that it is) (not done yet)
3 8 9 10 50 100 and the magic number is 583

Happy calculations.

MelodyFeb 6, 2014

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Melody:
Yes Stu you're right. There is just a scramble of ideas in here. This forum is very new. If you read through some of the 'end of day wrap up' posts you might get a better feel for what is happening in here. you can skip the credits, But i usually have something to say besides the credits each day.
Until 'I like Serena' arrived, on the 24th January, it was just me and the young people in this forum.
I had done very little foruming prior to this so if you find some of the setup in here bizarre. You are probably correct.
You've actually given me some good ideas. Why don't you read my nightly posts and become an integral part of our community?
Melody.

I liked what you did there with the number line Melody,
pretty sure that I might use that pretty soon

Since I don't know where to put them yet I thought I'd drop these two recources for percentages right here.

http://www.mathsisfun.com/definitions/percent.html
http://www.mathsisfun.com/percentage.html

They are pretty self explainatory

reinout-gFeb 6, 2014

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Guest:
Ask a Math Question!
6 4/5 - 2 1/4

6 4/5 - 2 1/4 = 34/5 - 9/4 (Since 6 = 6 * 1 = 6 * 5/5 = 30/5 => 6 4/5 = 34/5 and similarly for 2 1/4)
Now, to make the substraction we want to make sure that the denominators of both fractions are equal.
If we multiply 5 by 4 we get 20 and if we multiply 4 by 5 we also get 20.
Now lets first look at 34/5, if we are allowed to multiply the nominator and denominator with the same number to have it be the same number,

So (34*4)/(5*4) = 136/20

Then for 9/4 we have (9*5)/(4*5) = 45/20

Then 6 4/5 - 2 1/4 = 34/5 - 9/4 = 136/20-45/20 = 91/20

reinout-gFeb 6, 2014

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littlebeany99:
What is the length of a rectangle when it is 3 times the width and the perimeter is 96cm?

We know that the perimeter of a rectangle is two times the length plus two times the width.

So 2*length + 2*width = 96

Also, we know that the length of the rectangle is three times the width.

So length = 3*width

So for every length in equation 1 we can write 3*width, this makes;

2*3*width + 2*width = 96 => 8*width = 96 => width = 96/8 = 12

We know length = 3*width so length = 3*width = 3*12 = 36

hope that helped

reinout-gFeb 6, 2014

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Guest:
:x at a electronic store a tv costs $215 If the sales tax is 7% how much was the tv

I suggest you have a look at these two pages to have an idea about percentages

http://www.mathsisfun.com/definitions/percent.html

http://www.mathsisfun.com/percentage.html

Furthermore, what I miss in the question is whether the tv is $215 including the sales tax or without.

If the $215 is including the sales tax, then we know that 7% is sales tax and 100%-7% = 93% is the tv,

Hence $215*(93/100) = $199.95 would then be the price of the tv.

If the $215 is excluding the sales tax, then we know the tv costs an additional 7% of the initial amount.

Therefore the real price would then be 100%+7% of the original amount.

Hence $215*(107/100) = $230.05 would then be the price of the tv.

Look back into the question and see which one applies to your case.

reinout-gFeb 6, 2014

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Rom:
http://theotherdayatportrait.files.wordpress.com/2012/03/pi7.jpg

I like

We should add that to our resources

MelodyFeb 6, 2014

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maggot666:
https://docs.google.com/a/stu.irvingisd.net/document/d/1O-MfO_Jg8l5t7QuewObHqfTKsGIR4XsEz9ZgDWSeaso/edit answers to this please

That's a protected site. Access is denied.

MelodyFeb 6, 2014

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Yes Stu you're right. There is just a scramble of ideas in here. This forum is very new. If you read through some of the 'end of day wrap up' posts you might get a better feel for what is happening in here. you can skip the credits, But i usually have something to say besides the credits each day.
Until 'I like Serena' arrived, on the 24th January, it was just me and the young people in this forum.
I had done very little foruming prior to this so if you find some of the setup in here bizarre. You are probably correct.
You've actually given me some good ideas. Why don't you read my nightly posts and become an integral part of our community?
Melody.

MelodyFeb 6, 2014

#1

+118741

0

Guest:
How do I calculate the volume of 1x100000 infected parasites to give per 200ul/mouse and for 50 mice. The average number of uninfected is 8x1000000000.

I am sorry but this question doesn't make sense to me. I assume you have infected and uninfected parasites together in a solution. You have 10 ⁵infected parasites in how much solution???

MelodyFeb 6, 2014

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100 * (1 + 0.05) ¹²

to do it on the calculator type

1 + 0.05 = x ^y 12 * 100 =

RomFeb 6, 2014

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http://theotherdayatportrait.files.wordpress.com/2012/03/pi7.jpg

RomFeb 6, 2014