Rational Numbers, Rounding, and Order of Operations

Rational Numbers are any numbers that can be written as a fraction. That means: Integers Fractions Decimals

Rounding – Look to the right of the specified decimal place. If the number is 5 or greater, round up one. If the number is 4 or less, leave it alone. (You know this. You have been doing it forever!!!) Round to 3 decimal places look at the number to the right of the 6 it is higher than 5 so round up

Truncation – Cutoff what you don’t want. Approximate to 3 decimal places by truncation Cutoff everything past the “6” 7.456

Approximate to two decimal places by A) RoundingB) Truncation Approximate to two decimal places by A) RoundingB) Truncation Solution: 1. A) B) A) B) 23.02

You know this: PEMDAS Parentheses Exponents Multiplication Division Addition Subtraction Work left to right. If you see division before multiplication, that is okay do it first. Multiplication/division and addition/subtraction are done at the same time.

Example 1 7 – 2 * * 3 – 5 No parentheses or exponents, so look for multiplication/division 1 st. 7 – – 5Go back to the beginning to do addition/subtraction – 5 9 – 5 4

Example 2 -3(x – y) + 4(3x – 2y)Here there are parentheses, but you cannot combine anything. You need to distribute 1 st. -3x + 3y + 12x - 8y Now combine like terms 9x – 5y

Try a few on your own. Ask a partner if they are right, before I show you the answers * ÷ (5 + 3) + 7(3 – 2 * 5) 3. 3(5x – 2y) – 7(x – 3y) 4. 6x( ) – (3 * 2 ÷ 3) Solutions: x + 15y4. 18x - 2