CLASSWORK 2. Which of the balances in Sample B is the highest quality instrument? How do you know? The Exacto Balance is the highest quality instrument because it reads to the nearest tenth of a gram, which is more accurate (more exact place values) than any other balances. 3. Rock C is placed on the Econo-Balance. The balance reads 200 g. a. Does Rock C have a mass larger, smaller or the same as Sample A, or is it impossible to tell? Explain your reasoning. Rock C s mass is definitely larger than Sample A, because the Econo Balance rounded the mass of Rock B to 100 grams, while it rounded Rock C s mass to 200 grams. This means that Sample A is between 50-149 grams, while Rock C is between 150 and 249 grams. b. Does Rock C have a mass larger, smaller or the same as Rock B, or is it impossible to tell? Explain your reasoning. It is impossible to tell because the Econo Balance rounded both Rock B and Rock C to the nearest hundred and came up with 200 grams. this means that both Rock B and C are between 50-149 grams, but we can t be sure which is bigger. 1
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Classwork Homework Section 1. Memory Check - Rules! Please don t do this section in class - it won t do you as much good if you do it right after you learn it; but if you try tonight after your brain has had time to start forgetting you ll get more out of the recall! Try to fill in the blanks below (rules about which types of #s are sfs) from MEMORY. Then check yourself by checking the notes taped into your notebook from Handout 3a to make sure you remembered correctly! Always significant : 1) All Nonzero Numbers (example - 14 has 2 sf) 2) All zeroes that are Sandwiched between non zeroes (or decimals) (example - 2008 has 4 sf) 3) All zeroes that come after a decimal point AND at least one nonzero number (examples - 0.0280 has 3 sf, 3280.0 has 5 sf) Never significant : Zeroes that come after a nonzero number when there is no decimal or before a nonzero number when the number is 0.? (example - 3280.0 has 5 sf, 3280 has 3 sf) Section 2. Practice Counting SFs! (you are welcome to start this section in class) Section 3. Rounding Big Numbers! (you are welcome to start this section in class) Round 537,826.109 to the following place values: Hundredths: 537,826.11 Tenths: 537,826.1 Ones: 537,826 Hundreds: 537,800 Thousands: 538,000 Ten thousands: 540,000 3
Section 3. Practice Writing Multiplication ( ) & Division ( ) Answers Using SFs! (you are welcome to start this section in class) Model (Example) Problem - *The steps do not change if you are multiplying/dividing more than 2 numbers! 3 SF 4 SF (24.1) (8.001) =? Step 1 - Determine the # of SFs in each starting value. *notice how I annotated the # of sig figs in each # above the #!! Step 2 - Decide how many SFs should be in final answer by looking at the starting values. 24.1 has 3 sig figs, 8.001 has 4 sig figs So, my answer should have 3 sig figs because 3 is smaller than 4 (always take the lowest # of SFs). Step 3 - Solve the math operation w/a calculator Plug (24.1 / 8.001) into calculator & write whole answer (24.1 / 8.001) = 3.01212348 (EWW CALCULATOR DIARRHEA; THAT s NOT OUR FINAL ANSWER) Step 4 - Round the # from the calculator to the correct # SFs so that it s no longer gross 3.01 212348 in 3 SFs = 3.01 = final rounded answer 1. (0.32) x (14.50) x (120) =? 0.32 has 2 SF 14.50 has 4 SF 120 has 2 SF Therefore, the answer can only have 2 SF Un-rounded answer = 556.8 Rounded answer using SF = 560 2. (333) (0.00422) =? 333 has 3 SF 0.00422 has 3 SF My answer can only have 3 SF (from calculator) 333/0.00422 = 78909.9526 Rounded to 3 SF = 78,900 = FINAL ANSWER 4. (1.1) x (2.2) x (7.97) =? Decide how you will show your work! Must end up w/answer in correct # of sfs! 1.1 has 2 SF 7.97 has 3 SF 2.2 has 2 SF (from calculator) 1.1 x 2.2 x 7.97 = 19.2874 Rounded to 2 SF = 19.3 = FINAL ANSWER 3. (82.02) (0.0300) (400.0) =? 333 has 3 SF 0.00422 has 3 SF My answer can only have 3 SF (from calculator) 333/0.00422 = 78909.9526 Rounded to 3 SF = 78,900 = FINAL ANSWER 5. (800) x (7.0) =? Decide how you will show your work! Must end up w/answer in correct # of sfs! 800 has 1 SF 7.0 has 2 SF My answer can only have 1 SF (from calculator) 800 x 7.0 = 5600 Rounded to 1 SF = 6,000 = FINAL ANSWER 4
Extra Practice: Significant Figures Multiplication and Division: Determine the number of Sig. Figs in each of the following numbers. Complete the calculation and round your answer to the correct number of significant figures. 1. (11) (5.042) =? 4. (1.0) x (3.1) x (17.883) =? 11 has 2 SF 5.042 has 4 SF (from calculator) 11 / 5.042 = 2.186739 Rounded to 2 SF = 2.19 = FINAL ANSWER 2. (0.5) x (12.50) x (22.3) =? 1.0 has 2 SF 17.883 has 5 SF 3.1 has 2 SF (from calculator) 1.0 x 3.1 x 17.883 = 55.4373 Rounded to 2 SF = 19.3 = FINAL ANSWER 5. (1645) (0.022) (41)=? (from calculator) = 139.375 Rounded to 1 SF = 100 = FINAL ANSWER 3. (222) (0.0209) =? (from calculator) = 139.375 Rounded to 1 SF = 100 = FINAL ANSWER 6. (400) x (9.0) =? (from calculator) = 10622.0095694 Rounded to 3 SF = 10,600 = FINAL ANSWER (from calculator) = 3600 Rounded to 1 SF = 4000 = FINAL ANSWER 5