Transcript Estimating Decimals

Estimation
1.1
Essential Question: How can you judge the
reasonableness of the results of rational
number estimates and/or computations?
(SPI: 0606.1.2)
Think and Discuss
Suppose you are buying items for a
party and you have $50. Would it be
better to overestimate or
underestimate the cost of the items?
Vocabulary
Estimate: To find an answer close to
the exact answer by rounding, using
compatible numbers, overestimating
or underestimating, etc.
Rounding Rules
The digit to the right is greater or equal to
5, round up
The digit to the right is less than 5, round
down
Round each decimal to the indicated place
value.
Whole Number; 5.39 =
Tenths; 17.753 =
Hundredths; 3.761 =
Compatible Numbers
are numbers that are close in value to the
actual numbers, and which make it easy to do
mental math.
Estimate each sum or difference using
compatible numbers.
61.89 ÷ 9.26
524 x 32.654
5.99 + 3.76
17.19 ÷ 1.99
Essential Question
How can you judge the
reasonableness of the results of rational
number estimates and/or computations?
(SPI: 0606.1.2)
Problem Solving
Camera film costs $3.99 a roll.
Wes needs 3 rolls to take pictures
of the class party. He has $15.
Does he have enough money? If
not, then explain why?
Yes
Problem Solving
Alyssa wants to fill her swimming
pool.
It holds no more than 23 gallons
of water.
If her bucket holds 2 gallons, how
many will she need to fill without
overflowing the pool?
about 11 buckets
Problem Solving
Flowers cost $5.99 a dozen. Faye
wants to buy 2 dozen flowers. She
also wants to buy a balloon that cost
$4.50. Faye has $20. Does Faye have
enough money to buy everything she
wants? Justify your reasoning?
Yes
Problem Solving
Mike has math homework.
He has to do 4 rows of problems.
There are 9 problems in each row.
If he can do 10 problems every 15 minutes,
'about' how long will it take Mike to finish
his homework?
about 1 hour
Problem Solving
Eric bought pretzels for $1.89,
peanuts for $2.39, and popcorn for
$0.99. How much did he spend in
all? Explain how you reached your
conclusion?
Answer: $5.27
Exit Ticket
A total of 30 packages were mailed at a post
office on Saturday. The cost for each package
was between $5.55 and $6.30. Which best
represents the total cost for the packages mailed
on Saturday?
F more than $300
G between $200- $300
H between $100 and $200
J less than $100
Problem Solving
There are 9 groups at the beach.
The groups have an average of 18 people
each.
If the beach is supposed to have 2
lifeguards for every 150 people, how many
lifeguards should be on duty?
2
Problem Solving
A party is scheduled to last one
hour. Mrs. Call wants to show a
video that lasts between 10 to 15
minutes. About how much time will
be left for other activities?
Answer: about 45-50 minutes