MJ2

Ch 11.2 – Estimating Square Roots

Bellwork

• Police officers can use a formula and skid marks to determine the speed of a car. Use the formula below to calculate how fast a car was going if it left skid marks 83 feet long. Round to the nearest tenth. (s= speed, d=distance)

s

 39

d

Note: You do not have to write the question. However, your response should be in formula method format for full credit

s



s



s



s

 39

d

39(83) 3237

mph

Bellwork Solution

1. Write the formula 2. Substitute 3. Do the math

Assignment Review

• Text p. 472 # 13 – 33

Before we begin…

• Please take out you notebook and get ready to work….

• In the last lesson we looked at squares and square roots… • In today’s lesson we will look at estimating square roots…in order to estimate you will need to know the perfect squares….

Objective 11.2

• Students will estimate square roots

Estimating

• Generally speaking, students have a difficult time estimating…students do not have a fully developed number sense and really don’t get estimating… • The goal of estimating is to get a number that it is close to….we are not looking for an exact number here…the exact number is not important…

Estimating using a number line

• In the notes section of your notebook draw a number line.

• Plot the perfect squares from 1 through 12 on the number line • When estimating the goal is to find out which whole number the perfect square is close to… • That will be your estimate… • Let’s see what it looks like…

Number Line

• Your number line should look like this… • To find the square root of a number find where it fits on a number line • Then determine the two numbers it fits between • Determine which number it is closest to and look at the perfect square for that number 1 4 1 2 9 16 25 36 49 3 4 5 6 64 81 100 121 144 169 196 225

Perfect Squares

7 8 9 10 11 12 13 14 15

Example

Find the 75 The square root of 75 is between the square root of 64 and 81 Since 75 is closer to 81 than 64 the nearest whole number would be 9 1 4 1 2 9 16 25 36 49 3 4 5 6 64 81 100 121 144 169 196 225

Perfect Squares

7 8 9 10 11 12 13 14 15

Your Turn

• In the notes section of your notebook estimate each square root to the nearest whole number

Solutions

1. 39

6

2.

140

12

3.

106

10

Calculators

• You can also use a calculator to estimate a square root to the nearest whole number This is the square root key Input the square root number and press the square root key You will get a decimal for an answer. Round the decimal to the nearest whole number

Your Turn

• Using a calculator estimate the square roots to the nearest whole number 1.

2.

3.

131 277 3502

Summary

• In the notes section of your notebook summarize the key concepts covered in today’s lesson • Today we discussed: • Estimating square roots – how does that work?

• Using a calculator to estimate square roots – what do you do?

Assignment

• Text p. 477 # 13 – 28 Reminder • This assignment is due tomorrow • I do not accept late assignments • This is probably the only assignment that I will accept answers only!

• In this instance it’s kind of hard to show your work when you are using a calculator