Pages 144 150 Warmup Please write the Number Trick in words and in math language one step at a time Give your answer at the end Pick a number and then do the following operations in order Add 3 multiply by 7 subtract 4 divide by 2 and add 1 ID: 431368
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Slide1
2.8 – Undoing Operations
Pages 144 - 150Slide2
Warmup
Please write the “Number Trick” in words and in math language, one step at a time. Give your answer at the end.
Pick a number and then do the following operations in order: Add 3, multiply by 7, subtract 4, divide by 2, and add 1.Slide3
I Bet I can Guess Your Starting Number.
Do you think that if you told somebody your final answer, they can guess your starting number?
Tell Mr.
Schaner
your final answer and see if he can guess your starting number.
Learning Target:
In Investigation 2.8: Just Undo It!, we will figure out how to find anyone’s starting number if they go through the steps (correctly) of the “number trick.”Slide4
Investigation 2.8: Just Undo It!
We are going to solve an equation for
x
using a table.
Solve the following
equation
for x.
DescriptionSequenceExpression
Undo
Result
Pick a number
?
Divide by 4
Answer / 4
Add 7
Answer + 4
Multiply by 2
Answer 2
Subtract 8
Answer 8
Now let’s set this equation equal to 28 and solve for x.
28
36
18
11
44
Slide5
Partner Work: Do this problem with your partner
Solve the following by “undoing” the operations.
We start at
x
and work our way out to write the description
The number of rows needed = number of operations +1
Equation:
Expression
Description
Undo(Do the opposite)
ResultSlide6
Did I Get That? – 2.8
Using a table, find out what
x
is?
Equation:
Expression
Description
Undo
(Do the Opposite)
Result
42