Thinking Mathematically

Estimation and Graphs

Estimation

The process of getting an approximate answer to a question. Different situations require varying degrees of accuracy.

Examples: Giving a tip, buying enough beer for a party, or what you need on the final to get an A in a course.

Study Tip - “Place Value”

5 , 2 4 3 , 8 9 7

“Ones” place“Tens” place

“Hundreds” place

“Thousands” place

“Hundred Thousands” place

“Ten Thousands” place

“Millions” place

Graphs and Estimation

• Circle Graphs or Pie Charts [going from percent to numbers]

• Bar Graphs

• Line Graphs

“Rounding” NumbersTo “round” to a particular place:1. Look at the digit to the right of the digit

where rounding is to occur.

2. a. If the digit to the right is 5 or greater, add 1 to the digit to be rounded. Replace all digits to the right with zeros.

b. If the digit to the right is less than 5, do not change the digit to be rounded. Replace all digits to the right with zeros.

“Rounding”: Examples

“Round” 37 to the nearest “ten”.If the digit in the place to the right is 5 or greater, add 1 and replace all digits to the right with zeros.

40

What if it said “round to the nearest 100?

Estimation Examples

You select 4 items at a store costing $2.56, $4.44, $3.95, $7.22. You have only a twenty dollar bill. Do you have enough?

A woman makes $48,343 a year. Estimate her monthly salary. Estimate her weekly salary.

Other Estimation Techniques [Pass out handouts and use estimation notes for previous text]

Compatible Numbers x Compensation 48-29 49-30 19Front end 278 + 642 200 + 600 = 800 53x49 50x40 = 2000Rounding: up, down, on 5Range: 278 + 642 200 + 600 = 800 278 + 642 300 + 700 = 1000 Range estimate is 800-1000