Rounding & Significant Figures

August 28th & 29th, 2013

Warm Up

• Complete notes on types of numbers from last class!

• Think about WHY we need/should round numbers…

If a traffic survey showed that 1852 cars carried 4376 people, the average person per car would be 2.362850972

SAY WHAT?!?!?

Rounding Numbers

How to round a number:• If the digit after the one being

rounded off is LESS than 5, we round DOWN

(i.e. 0, 1 , 2 , 3 , or 4)• If the digit after the one being

rounded off is 5 or MORE than we round UP

(i.e. 5,6,7,8,9)

Examples

Round to the nearest 10:• 48

• 583

• 5705

Exercises

• Complete #1-3 on page 75 if you have Edition 2

• Complete #1-3 on page 45 if you have Edition 1

Using some real facts & figures!Round off to the accuracy given:

• The cost of an overseas holiday is $15,387 (to nearest $1000)

• The mass of a horse is 468 kg (to ten kg)

• A distance of 5735 km (to nearest 100 km)

• Box office takings for new movie were $6,543,722(to nearest hundred thousand)

Rounding Decimal Numbers

• We need to round off decimal numbers which have more figures in them than are required. (Example: MONEY!)

• We can round off to the certain number of decimal places or significant figures.

• What is a significant figure?

Examples

Round:• 3.27 to one decimal place

• 6.3829 to two decimal places

• 9.0456 to three decimal places

Exercises

• Complete #1-2 on page 77 if you have Edition 2

• Complete #1-3 on page 47 if you have Edition 1

Significant Figures

• ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant.

• ALL zeroes between non-zero numbers are ALWAYS significant

• A final zero or trailing zeros (in the decimal portion only) are significant

http://www.youtube.com/watch?v=ZuVPkBb-z2I

Examples

7.182 ≈ 7.2 (2 sig figs)

0.00132 ≈ 0.0013 (2 sig figs)

423 ≈ 400 (1 sig fig)

4.057 ≈ 4.06 (3 sig figs)

Exercise

• EDITION 1: #1-4 & 6 page 48-49

• EDITION 2: #1-4 page 78

Homework!

Finish all exercises from this power point & turn in!

1-3 Rounding1-2 Decimal Rounding

1-4 (& 6 Edition 1) Significant Figures