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 Read notes 11-12 and watch the video on scientific notation before day 6 (1.04 notation)

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

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

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!

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!

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!)

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!”

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

Look in your packet

Look in your packet

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

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.

Examples in your packet

Examples in your packet

Another example

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

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)