I have a Chemistry question which should be very simple but I do not know what significant figures are.

Assuming the following numbers are measurements and using the rules for significant figures, determine the answer for the following calculation.

(15.5/42)*219.5=

1. 81.0059
2. 81.006
3. 81.01
4. 81.0
5. 81

The number obtained from the calculator is 81.00595238 should I just round or are significant figures something else entirely?

Here is a good site to read about s.f.

http://www.chemteam.info/SigFigs/SigFigs.html

15.5 has 3 s.f.
42 has 2 s.f.
219.5 has 4 s.f.
This is a multiplication/division problem.
So the answer may have no more than xxxx s.f.; therefore, the answer is xxxxx.

Thanks a lot!

Significant figures are a way to indicate the accuracy of a measurement or calculation. They help ensure that the final answer reflects the precision of the original measurements.

When performing calculations using significant figures, there are a few rules to follow:
1. Non-zero digits are always significant.
2. Any zeros between non-zero digits are also significant.
3. Leading zeros (zeros at the beginning of a number) are not significant.
4. Trailing zeros (zeros at the end of a number after the decimal point) are significant.
5. Trailing zeros before a decimal point are significant only if the number contains a decimal point.

Let's go through the calculation step by step.

(15.5/42) = 0.369047619 (rounded to 9 decimal places) or 0.369 (rounded to 3 decimal places based on the smallest number of decimal places in 15.5/42)

0.369 * 219.5 = 80.918 (rounded to three significant figures based on the smallest significant figures in 0.369 and 219.5)

Therefore, the answer to the calculation (15.5/42)*219.5 is 81.0 (Option 4).

When reporting the answer with the correct number of significant figures, we round the final value. In this case, the answer from the calculator, 81.00595238, should be rounded to 81.0 since there are only three significant figures in the original calculation.

Significant figures are a set of rules used in scientific measurements to indicate the precision or uncertainty of a measured value. They help convey the accuracy of a measurement and ensure that the calculated result does not imply more precision than the original data.

To determine the answer for the given calculation using significant figures, you need to follow these rules:

1. Non-zero digits (1-9) are always significant. For example, the number "15.5" has three significant figures.

2. Zeros between non-zero digits are significant. For example, the number "219.5" has four significant figures.

3. Leading zeros (zeros to the left of the first non-zero digit) are not significant. For example, the number "0.0042" has two significant figures.

4. Trailing zeros (zeros to the right of the last non-zero digit) may or may not be significant, depending on whether a decimal point is present. For example, "100.0" has four significant figures, while "100" has only one.

To determine the answer for the given calculation (15.5/42)*219.5=, we need to apply the rules:

Step 1: Calculate (15.5/42) = 0.369047619 (as obtained from the calculator).

Step 2: Multiply the result by 219.5: 0.369047619 * 219.5 = 81.00595238.

Step 3: Since the original numbers used in the calculation have different numbers of significant figures, the answer should be rounded off to match the least number of significant figures. In this case, "42" has two significant figures, so the final answer should also have two significant figures.

Therefore, the correct answer, rounded to two significant figures, is:

Option 3. 81.01

So, you should choose 81.01 as the answer to the calculation.