Measurements

Description and Measurement

Chapter 2:1

Pages 42-49

Measurement

A way to describe the world with numbers Answers questions such as how long, how

much, or how far.

Estimation

A rough measurement of an object You use prior knowledge to help you with an

estimation Comparison is a good way to create an estimation

Used to check if your answer is reasonable Use the word “about”

Precision and Accuracy Precision is a description of how close measurements are to

each other …The SMALLER the measure the MORE precise EX: a second hand is more precise than a minute hand

Accuracy is when you compare a measurement to a real, actual, or accepted value.

EX: a watch which is not set correctly is NOT accurate

Rounding

If the digit to the right is 0,1,2,3, or 4, the digit being rounded stays the same

If the digit is 5,6,7,8, or 9, the digit rounded increases by 1

The digits to the right of the digit being rounded to are deleted if they are also to the right of the decimal. If they are to the left of the decimal, they are changed to zero.

How we would round to the tens place? 1579.254 28.888 17359.8882

Rounding Examples

Round 217 to the nearest hundred Round 800 to the nearest hundred

Round 564 to the nearest tenRound 295 to the nearest tenRound 725 to the nearest ten

Round 959 to the nearest hundredRound 252 to the nearest ten

Round 618 to the nearest hundredRound 928 to the nearest ten

Round 732 to the nearest hundredRound 163 to the nearest tenRound 21 to the nearest ten

Significant Digits

Example # of Significant

Digits

Rule

453 3 All non-zero digits ARE always significant

5057 4 Zeros between 2 significant digits ARE significant

5.00 3 Additional zeros to the right of decimal and a significant digit ARE significant.

0.007 1 Placeholders are NOT significant

0.0002030 4 Initial (beginning zeros) are NOT significant

The number of digits that truly reflect the precision of the number are called significant figures. The Rules are as follows:

Mrs. Schremp Note To Self:

Copy previous slide onto a notebook and do examples.

Rules for Sig. Figs.

For multiplication and division, you determine the number of sig figs in each number of your problem. The sig figs of your answer are determined by the number with the fewest digits.

EX: 6.14 X 5.6=34.384 For addition and subtraction, you determine the place value of

each number in your problem. The sig figs of the answer are determined by the number that is least precise. (using tens, hundredths, etc.)

EX: 6.14 + 5.6=11.74

Homework