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Do Now

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. Todays Goal. Become experts at rounding math problems to the correct precision/sig figs Homework: (before the class after next) Finish Rounding Homework

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Do Now

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  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 11-12 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 11.003 km as the answer • THIS WOULD BE WRONG!

  6. Why? • 11km is only precise to the kilometer. It could actually be 11.427 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 11.003 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 + .003 km • Least precise place is the ones place, so we will round to the ones. • 11km + .003 km = 11.003 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 - 17.0 ml = 153.0 ml after rounding • 150 ml • 17g/ml x 5ml = 85 g after rounding • 90g • 2134g / 17.6ml = 121.25 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 11-12 and watch the video on scientific notation before day 6 (1.04 notation)

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