## elisichi 2 years ago Math question! Help please! Semester test tomorrowww!!

1. elisichi

There it is :(

2. elisichi

The answer for part B, the one I don't get is 3050, but I don't know how to get there.

3. mathstudent55

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Who told you the answer for B is 3050? That's not what I came up with.

Even though that's a REALLY big number, I realize I forgot to calculate the internal diameter. Hold on.

Okay. I think I've got the answer. Can you tell me how you started this problem?

7. elisichi

The textbook says that..

Textbook's wrong. Over THREE THOUSAND washers can be carved from one square meter of metal?

9. elisichi

Yes, so I did 3/0.0004= 7500 and thats the number of washers for question a

How did you get .0004?

11. elisichi

Oh my gosh, never mind I get it!!

What do you get?

You know the formula for the area of a circle is (3.14 * r^2) ? That's why I have no idea where you got the .0004

14. elisichi

So it is 3050 :)

What's 3050?

Here's what I did: I figured out the diameter of the entire washer. The washer's EXTERNAL DIAMETER is 2 cm. That means that the radius is 1 cm. And that means that the area is 3.14 cm squared, which is the same as .0314 meters squared.

I found the AREA of the entire washer, sorry. That's .0314 meters squared.

But the washer has a hole. So now we have to find the area of the hole. The DIAMETER of the hole (INTERNAL diameter) is 1 cm. That means that the AREA of the hole is.... (3.14 * .5 squared), which is .785 cm squared.

If you subtract that from 3.14 cm squared, you get 2.36 cm squared, which is the same as .0236 meters squared.