1-20 The Mean Old Average

1-20 The Mean Old Average

Introduced in L55

Warm Up

Lana's quiz average was 87.5%. If she scores 86% on her next quiz, will her new quiz average be more or less than 87.5%? How do you know?

Open Ended

Lana's quiz average was 87.5%. If she scores 86% on her next quiz, will her new quiz average be more or less than 87.5%? How do you know?

Learning & Habit Objectives

Learning: I will solve problems involving the mean

Habit: I will think flexibly

Success Criteria

• I know the mean formula

• I can reason about the sum, size and mean

• I can think flexibly to solve different problems involving the mean

Notebook: The Mean Formula

Example 1 If the sum is 256 and the size is 8, find the mean.

Example 2 If the mean is 120 and the sum is 600, find the size.

Notebook: Finding a Missing Part of the Sum (will do in class)

The mean of three numbers is 45. Two of the numbers are 52 and 56. Find the third number.

Multiple Choice

The formula for mean is

• $mean\ =\ \frac{product}{size}$

• $mean\ =\ \frac{sum}{size}$

Multiple Choice

In the formula for mean, size is the...

• product of the numbers

• difference of the numbers

• number of numbers in the set

Fill in the Blanks

The average of four numbers is 82. Three of the numbers are 100, 75 and 80. What is the fourth number?