## Tuesday, January 19, 2010

### Problems & Percents

Problems & Percents

We will use example 4: Determine a Percent
This example uses PROPORTIONS in this problem.
To solve this problem we will do part a.
a)What percent is the current speed of the original speed?
For this we will use proportions to help us.
We need to find the CURRENT speed over the ORIGINAL speed.

Now we need to find the original speed and current speed.
The current speed is at 50 km/year.
The original speed was at 10 km/year.

Now you can see here the current speed is 50 km over 10 km (Current Speed over Original Speed)
Now we need to find what percent of the current speed is over the original speed.
10 km is 100%
How do you get from 10 km to 50 km?
10 x 5 = 50 km
So we do the same thing we do to the percent.
100% x 5 = 500%

Here is the answer to a.
The current speed is 500% over the
original speed.

Now we will do b.
In this question we're finding how much the pole drifts in 1 year around the earths circumference in percent form.
We know that the pole drifts 50 km / year.
The Earths circumference is 40 000 km.
We will also be using proportion for this.
We need to find the poles km over the earths circumference.
So it will be 50 km over 40 000 km.
Now we will need to simplify this into lowest terms.
The answer we get is 1 / 800
Now we can find the percent by dividing 1 by 800.
1/800 = 0.00125
To get the percent we need to multiply the decimal by 100.
0.00125 x 100 = 0.125%.

So the answer is that at 50km / year the pole drifts 0.125% or 1/8% of the Earths circumference in 1 year.

Eric.P 8-73

Good job it helped me.

Alexander8-73

Nice job Darnell good job explaining

Jemineth873

Good job darnell, your explanation was clearly understandable and well described .

vicky873

Good job on explaining.

vicky873

Good job on explaining.

Camille873

great job darnell i liked how you put pictures then the question and answer great job darnell keep up the good work. (:

Abigail8-73

Good job Darnell! I like how you make the explanations simple and how you took your time to put up a picture. Good job again! (:

hannah873

Your explanation was very thoughtful and clear. And I like how you made the important words stand out for more emphasis. The pictures helped as well. Job well done.