5McKie Rounding and Estimating Study Guide1.
2.
3.
4.
Work through the explanations and examples.
Answer the Practice questions.
Look at your answers to fill in the column A below.
See which areas you still need to work on & see Mrs.
McKie for more explanation & practice. Fill in Column
B with what you did to improve.
Target
Name: ___________________
ND
You don’t get it yet
1
You’re beginning to get it
2
You’ve got the basics and you’re nearly there
3
You’ve got it
4
You are a master and an expert
A
How well
prepared do
you feel for
these questions
on a quiz?
1
2
3
4
5
6
Rounding to the nearest ten or
hundred
Rounding to the nearest thousand or
ten thousand
Rounding to the nearest hundred
thousand
Estimating: Front End Rounding
Strategy
Estimating: Compensation Strategy
Estimating: Compatible/ Friendly
Number Strategy
B
What did you do to help improve your
understanding?
Rounding
Step 1
Find the place you want to round to.
Underline the digit in that place.
Step 2
Step 3
Look at the digit to its right. Circle
that digit.
5 843
5 843 rounds to 6 000
5 843
Rounding to the nearest ten or hundred
Round these numbers to the nearest ten.
a.
c.
e.
g.
1 305
450 031
7 858
9 009
b.
d.
f.
h.
345
72 374
590 002
7
b.
d.
f.
h.
780
3 567
2 125
3 009
Round these numbers to the nearest hundred.
a.
c.
e.
g.
1 799
3 045
1 498
2 800
*If the circled digit is 5 or greater (5,
6, 7, 8, or 9) round up.
*If the circled digit is less than 5 (4, 3,
2, 1, or 0), round down.
*8 is greater than 5 so round up.
Rounding to the nearest thousand or ten thousand
Round these numbers to the nearest thousand.
i. 1 305 255
k. 450 031
m. 7 800
o. 9 000 407
j.
l.
n.
p.
345
72 370
590 002
7
j.
l.
n.
p.
11 780
3 567
2 125
35 009
b.
d.
f.
h.
8 944 780
345 567
299 125
3 551 009
Round these numbers to the nearest ten thousand.
i. 112 799
k. 302 045
m. 145 498
o. 222 800
Rounding to the nearest hundred thousand
Round these numbers to the nearest hundred thousand.
a.
c.
e.
g.
100 799
335 045
198 498
2 765 800
Estimating: Front End Rounding Strategy
Front-end Strategy
The front-end strategy is a method of estimating computations by keeping the first digit in each of the
numbers and changing all the other digits to zeros. This strategy can be used to estimate sums and
differences. Note that the front-end strategy always gives an underestimate for sums.
Example: 123 + 212= 100 + 200 = 300
You can choose to round to the 1st digit or the 1st 2 digits. (Not allowed to use calculators.)
a. 257 + 945 =
b. 5 459 + 4 892 =
c. 13 456 - 346 =
d. 12 349 - 951 =
Estimating: Compensation Strategy
Compensation Strategy
The compensation strategy is a method of adjusting a computational estimate to make it closer to the
calculated answer. This strategy is used with the front-end rounding and compatible numbers strategies to
provide better estimates.
Example: You buy a hamburger for $4.79 and a drink for $1.26. Will a $5 bill cover the cost? (Solution:
$4.79 + $1.26)
Front-end rounding: $4 + $1 = $5
Compensation: $0.79 and $0.26 = $1
$5 + $1 = $6
Answer: A $5 bill will not cover the cost because the cost is a little more than $6.
a. 10 532 + 14 399 + 18 221 =
b. 2897 - 911 =
c. $12.29 + 13.11 =
d. $127.98 + 257.23 + $478.20 + 613.42 =
Solving real-life problems using a suitable
strategy and explaining your thinking.
ND
1
For each problem, tell me:
• Which strategy did you choose?
• Why did you choose it?
• What were the steps that you followed?/ What did you do?
A) Two games were played in the semi-finals of a soccer tournament.
The attendance at one game was 18 595.
The attendance at the other game was 19 240.
i) How many people attended to semi-finals? (actual)
ii) Check that your answer is reasonable. (estimate and compare)
2
3
4
B) Members of the school council have raised $10 500.00.
They plan to buy sports equipment for $3 985 and library books for $7 54.00.
i)
ii)
Predict whether the council raised enough money to make the purchases.
Compare you prediction with the actual.