Sometimes it makes
more sense to underestimate.
Sometimes an overestimate is more
reasonable.
Solve
the problem using the flowchart. 
Lisa wants to
buy a shirt that costs $9.95 and a sweater that costs $18.25. She
has $13.20 that she has saved and $25.40 from babysitting.
Does she have enough money? 
Start

Use the
flowchart below to choose and apply estimation methods. 
Underestimate,
round down.
To
be sure that Lisa has enough money, underestimate.
You want your estimate to be less than what Lisa
actually has. 
Round
down the money she has. 
$13.20


$10.00 
$24.25


$20.00 
$10
+ $20

=

$30.00 


Overestimate,
round up.
Overestimate
the cost of the shirt and sweater. This way your estimate
will be more than the actual cost. 
Round
up the cost of the shirt and sweater. 
$9.95 

$10.00 
$18.25 

$19.00 
$10
+ $19 
= 
$29.00 
Since Lisa has about $30
and the shirt and sweater cost about $29, she has enough
money. 


Read
all the information to determine whether to underestimate or
overestimate. Then find the facts you need.
To
Underestimate,
round down.
To Overestimate, round up. 
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