1. OOPS! MY BAD!
By Catherine D

2. Penny My guess was that the diameter of the penny was 16mm(1.6 cm)
I had measured the penny and got 1.6cm. Using a proportion of 10mm over 1cm=Xmm over 1.6cm, solving it for 16mm.
Then, I did some research and found that a penny is actually 19.05mm.
So, now I had to find my percent of error.

3. Penny Continued
First, I had to find the difference between the amounts, which was 3.05mm.
Then, I divided 3.05 by and got .1601
Finally , I rounded to the nearest tenth of a percent
My final answer was 16% of error

4. Nickel My guess was that the diameter of the nickel was 20mm(2cm)
I had measured the nickel and got 2cm. Using a proportion of 10mm over 1cm=Xmm over 2cm, solving it for 20mm.
Then, I did some research and found that a nickel is actually 22mm.
So, now I had to find my percent of error.

5. Nickel Continued
First, I had to find the difference between the amounts, which was 2mm.
Then, I divided 2 by 22 and got .0909
Finally , I rounded to the nearest tenth of a percent.
My final answer was 9.1% of error

6. Quarter My guess was that the diameter of the quarter was 22mm(2.2cm)
I had measured the quarter and got 2.2cm. Using a proportion of 10mm over 1cm=Xmm over 2.2cm, solving it for 22mm.
Then, I did some research and found that a quarter is actually 24mm.
So, now I had to find my percent of error.

7. Quarter Continued
First, I had to find the difference between the amounts, which was 2mm.
Then, I divided 2 by 24 and got .0833
Finally , I rounded to the nearest tenth of a percent.
My final answer was 8.3% of error

8. Formulas I used The formulas I used were: Unit Conversions: 1cm=10mm
Percent of Change: The amount of change divided by the original amount

9. Observations
1: In order to get the most accurate measurement, you need to make sure you are measuring in the center of the coin.
2: On the quarter, I had the lowest error between measurement and actual because it is such a big coin.
3: On the penny, I had the largest error because it is so small.