1. Do Now
How many sig figs are in the following numbers and what is their precision:
34.20 g
20.0 m
.0032 km
.2003 g

2. Todays Goal
Become experts at rounding math problems to the correct precision/sig figs
Homework:(before the class after next)
Finish Rounding Homework
Read notes and watch the video on scientific notation before day 6 (1.04 notation)

3. What is precision?
Is 7.0 cm the same thing as 7.00 cm?

4. Is 7.0 cm the same thing as 7.00 cm?
No, and here is why;
Think back to the measurement lab. The precision of your measurement depended on the tool you were using VS
7.00 cm
7.0 cm VS

5. Why is precision important?
Comes into play when you need to do math
For example;
If you added 11 km and .003 km you may be tempted to put km as the answer
THIS WOULD BE WRONG!

6. Why?
11km is only precise to the kilometer. It could actually be km (or some other measurement) but the instruments could not read that precise.
11.???????, don’t know what those numbers are!

7. Why?
If you put your answer as km you are saying that all your measurements were precise to the thousandths place (WHICH THEY WEREN’T!)

8. So what is 11km +.003km?
To answer that, you will have to do some rounding
You always want to round to the least precise measurement place when adding/subtracting
“WHEN ADDING OR SUBTRACTING NUMBERS, RIGHT THERE IN YOUR FACE LOOK FOR THE ONE THAT’S LEAST PRECISE AND ROUND IT TO THAT PLACE!”

9. 11km km
Least precise place is the ones place, so we will round to the ones.
11km km = km  11 km

10. Look in your packet

11. Look in your packet

12. Examples in the notes
A) take a look, what is the least precise number there?
Tenths
Final measurement is rounded to the tenth
B) thousandths
C) Hundreds

13. What if we multiply/divide?
IF YOU HAVE SOME MEASUREMENTS TO MULTIPLY OR DIVIDE, ROUND TO THE FEWEST SIG FIGS, COUNTING FROM THE LEFTWARDS SIDE!
In other words, you want to keep the lowest number of sig figs.

14. Examples in your packet

15. Examples in your packet

16. Another example

17. Practice 20.1 g + 60.33 g = 60.43 g After rounding 60.4 g
170 ml ml = ml after rounding
150 ml
17g/ml x 5ml = 85 g after rounding
90g
2134g / 17.6ml = g/ml rounding
121g/ml

18. Rounding homework Get started on it! Run into trouble?
Ask a neighbor (they’re closer after all)
Ask me!
When your finished, have me check it
HW: Read notes and watch the video on scientific notation before day 6 (1.04 notation)