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Journal 8/26/14

Journal 8/26/14. Let’s say you need to know the temperature outside before you get dressed for the day. You ask a friend. He says “It’s about 50 degrees. I dunno . Maybe more, maybe less.” How could this be more useful or helpful?. Objective Tonight’s Homework.

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Journal 8/26/14

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  1. Journal 8/26/14 Let’s say you need to know the temperature outside before you get dressed for the day. You ask a friend. He says “It’s about 50 degrees. I dunno. Maybe more, maybe less.” How could this be more useful or helpful? Objective Tonight’s Homework To understand how to mathematically manipulate measurements pp 37: 5, 6, 7, 8, 9

  2. Notes: Significant Figures Last time, we saw how to properly get the precision of a measurement. Today, we’ll talk about how we can manipulate these numbers – addition, subtraction, multiplication, division.

  3. Notes: Significant Figures In addition and subtraction, we must round all numbers to the same decimal as the least precise number. Example: Add the following: 32.11 meters 76.8 meters 4.103325 meters 32.11 76.8 4.103325 113.013325 113.0 meters

  4. Notes: Significant Figures Multiplication and division are harder… To start, we have to know how many significant digits or figuresa measurement has.We use the following rules to find how many significant digits we have. 1) Non-zero digits are always significant 2) Zeros after a decimal point that are also after non-zeros are significant 3) Zeros between other significant digits are significant 4) Zeros used just to space the decimal point are not significant

  5. Notes: Significant Figures Examples: 143.33 15,250,000 0.0000243 0.00003001 10,000.1 0.00050

  6. Notes: Significant Figures Examples: 143.33 5 significant digits 15,250,000 4 significant digits 0.0000243 3 significant digits 0.00003001 4 significant digits 10,000.1 6 significant digits 0.00050 2 significant digits

  7. Notes: Significant Figures Think of significant digits like this… It’s a way of measuring how many digits in a number are important or not-rounded. If I say 10,000,000 people, anyone reading this knows it’s not exactly 10,000,000 people, but something rounded. But if I say 10,000,001 people, suddenly we don’t assume rounding any more. Why not? Because otherwise why would we have changed the end to a 1 if it didn’t mean something? Keep this in mind. It makes things easier.

  8. Notes: Significant Figures So how do we use this? When multiplying and dividing, we round everything to the number of significant digits in the least precise measurement.

  9. Notes: Significant Figures So how do we use this? When multiplying and dividing, we round everything to the number of significant digits in the least precise measurement. Example: 21.7 meters x 1,000 meters 3 sig figs 1 sig fig 21,700 meters  20,000 meters We round to 20,000 because “1,000 meters” had only one significant digit.

  10. Practicing Significant Figures Let’s practice these concepts. Work with a partner and do the following problems. pp 37-38: 10, 11, 12, 13, 14, 15

  11. Exit Question #5 What is the proper value of 3.22 cm times 2.1 cm? a) 6.762 cm2 b) 6.76 cm2 c) 6.8 cm2 d) 7 cm2 e) None of the above

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