Rounding

[Shreya Patel- 2D]

When should we round our answer in a problem? For example, if it's a two step process, is it okay to round within the problem?

[Sahaj Patel Lec3DisK]

I assume you are talking about rounding sig figs. In that case, you should round your final answer. Until then, use numbers that are exact as possible.

[Q Scarborough 1b]

Like what was said above, you should wait to round until the final answer. If you round before then, especially if the question has many steps, you can cause your answer to be skewed.

[Brenda Silva 1B]

When solving a problem with multiple steps, such as a two step problem, try using the exact values throughout your calculations and only round your final answer, this would allow you to have an accurate result.

[Darren1j]

Some elements of the periodic table have 4 sig figs as their molar mass and others have far more. When calculating the molar mass of a compound, how many sig figs should there be or number be rounded to?

[George Hernandez 3I]

If it's not too confusing, try to use the most exact values as you possibly can and round at the end. This way, you won't have much dispairity to the actual answer. If you round your values throughout the problem, as you work through it, you may expect a solid whole number at some point but actually calculate 2.8, so you'll have to assume that it's '3' that you're looking for.

[Aria Movassaghi 1A]

For me, the easiest way is to use exact numbers all the way until the final answer and then round that answer. This way, you don't have to worry about your final answer being slightly off.

[Chem_Mod]

Please do not round until the end! If you are using a calculator it should be fairly easy to store the values.

[Sara_Lim_2C]

A friend of mine heard this rounding rule in her chemistry class (not at UCLA):

"If the digit removed is 5, the preceding number increases by 1 if it is odd and remains the same if it is even: 17.75----->17.8; 17.65----->17.6"

Neither of us had ever heard of it before, has anyone else? Is this a widely used rule or are there just certain institutions that might use it?

[Jason_Glass_2L]

You are probably going to want to keep the most accurate values until the final answer. If you want to make things easier, if you know the answer would be 4 sig figs, I would round the numbers before to 5 to six sig figs to stay safe of missing the answer by a 0.001. Another thing you can do is use you calculator and use the ans function so it uses the exact number and carry on through the problem using the ans function.

[Eliana Carney 3E]

You should wait to round until the last step of the problem for the most accurate answer. Personally, I keep the values stored in my calculator and use the stored values for further calculations within the problem. This saves you the time of having to retype precalculated values.

[Carly_Lipschitz_3H]

A friend of mine heard this rounding rule in her chemistry class (not at UCLA):

"If the digit removed is 5, the preceding number increases by 1 if it is odd and remains the same if it is even: 17.75----->17.8; 17.65----->17.6"

Neither of us had ever heard of it before, has anyone else? Is this a widely used rule or are there just certain institutions that might use it?

Hi Sara! I've never heard of that rounding rule either. I always prefer to wait until I'm done with my calculations and am at the very end to round my final answer. By keeping as many sig figs throughout my calculations as possible, I find that my answers are as accurate as possible. I'm not sure how well that rounding rule would work.

[alexandralopez 3F]

i agree with everybody else who replied. Your best bet is storing the numbers and rounding only until you have your final answer.

good luck!

[Liam Bertrand 3]

Thanks for the advice, I'd been rounding as you would in a math class and my answers were a bit off. Thanks!

[Ralph Zhang 2L]

The way I always do it is writing down all the steps first, then keep it all in the calculator until the final step, where you round to the required sig figs.

[Gerardo Ortega 2F]

If the problem has multiple steps, you should leave the values you get after each step in your calculator and round at the very end to ensure that your final answer is as accurate as possible.

[Sabrina Galvan 3J]

Some elements of the periodic table have 4 sig figs as their molar mass and others have far more. When calculating the molar mass of a compound, how many sig figs should there be or number be rounded to?

For molar masses, typically the most sig figs that should be accounted for in the compound is four. However, still be sure to look for other values within the problem that have less than the equivalent of four sig figs, as they will be the determining amount of sig figs found in your final answer.

[Abraham De Luna]

Normally you would want to wait until the final answer before you round.

[Brandon McClelland3L]

Try to use the most exact numbers possible until you submit your final answer. Then, use sig figs to determine how much you have to round.

[Bai Rong Lin 2K]

Are we suppose to always round to maintain the same sig figs?

[Blas_Rodriguez_1B]

you would round your final answer to avoid any mistakes as you continue to do your work and to keep the answer as precise as possible.