# Chemistry: Significant Figures and Addition

• Soaring Crane
In summary, the conversation discussed adding numbers with different significant figures and determining the correct number of significant figures in the final answer. The final answer for the addition problem with 5 decimal place numbers and 2 significant figures was determined to be 0.0003. One person also made a mistake in the addition, but ultimately both individuals gained a better understanding through the discussion.
Soaring Crane

## Homework Statement

I just wanted to know if I wrote the answer with the correct number of significant figures for this addition problem.

0.00015 M + 0.00004 M + 0.00011 M = 0.00030 M (Correct?)

## Homework Equations

See above.

0.00015 M + 0.00004 M + 0.00011 M = ?

## The Attempt at a Solution

See Part 1.

All of the original numbers have 5 decimals places, but only the first and third values have 2 significant figures. (The second has 1 significant figure.) Therefore, the final answer must be expressed with 5 decimal places, and will have 2 significant figures (0.00030 M)?

Thank you.

You have all the place values known to the fifth decimal place, so yes, take to the fifth decimal place.

I would say that the answer was 0.0003. If you were to express the answer to 5 places you would get 0.00029... that is two sig figures and you are allowed one. 0.00030 has two sig figures and you are allowed one.

0.111+0.222+0.0001=0.3 then?

Borek said:
0.111+0.222+0.0001=0.3 then?

Yikes! Of course you are correct, Borek. Good catch. You will also note that I cannot even be trusted to correctly add three numbers together as well...

We each did some rethinking and are a bit better for doing so.

haha should you really be helping people with that kind of math? XD just kidding :P

Sometimes I amaze myself.

chemisttree said:
Sometimes I amaze myself.

Don't feel alienated

## What are significant figures in chemistry?

Significant figures in chemistry refer to the digits in a number that represent the precision of a measurement. In other words, they are the meaningful digits in a number that convey the accuracy of a measurement.

## Why are significant figures important in chemistry?

Significant figures are important in chemistry because they represent the precision of a measurement, which is crucial in accurately reporting and communicating scientific data. They also help to minimize the potential for error and ensure consistency in calculations.

## How do you determine the number of significant figures in a number?

To determine the number of significant figures in a number, follow these rules:

1. Non-zero digits are always significant.
2. Any zeros between two significant digits are significant.
3. Leading zeros are not significant.
4. Trailing zeros are significant only if there is a decimal point.

## What is the rule for adding and subtracting with significant figures?

The rule for adding and subtracting with significant figures is that the result should have the same number of decimal places as the measurement with the fewest decimal places. For example, if adding 3.2 and 1.75, the result should be reported as 4.0 because 3.2 has one decimal place and 1.75 has two decimal places.

## How do you round a number to the correct number of significant figures?

To round a number to the correct number of significant figures, follow these rules:

1. If the digit to the right of the last significant figure is less than 5, round down.
2. If the digit to the right of the last significant figure is 5 or greater, round up.
3. If the digit to the right of the last significant figure is exactly 5, round up if the last significant figure is odd, or round down if the last significant figure is even.

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