Decimal Form Of Rational Numbers Worksheet - Chapter 2.2, Mathlink 9, Mcgraw-Hill Ryerson School Page 2
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8Link the Ideas
Example 1:
Add and Subtract Rational Numbers in Decimal
Form
Estimate and calculate.
2.65 + (-3.81)
a)
-5.96 - (-6.83)
b)
Solution
Estimate.
How does the number
a)
line show the estimate?
2.65 + (-3.81)
−4
≈ 3 + (−4)
3
≈ -1
−2
−1
+1
+2
+3
0
Method 1: Use Paper and Pencil
Calculate.
Adding the opposite of 3.81 is the same as subtracting 3.81.
2.65 + (-3.81) = 2.65 - 3.81
Determine the difference between 3.81 and 2.65.
3.81 - 2.65 = 1.16
However, 2.65 - 3.81 must be negative, since 3.81 > 2.65.
So, 2.65 + (-3.81) = -1.16.
Method 2: Use a Calculator
Tech Link
Calculate. C 2.65 + 3.81 + -
= –1.16
The key for entering a
negative sign may look
Estimate.
How does the number
b)
diff erent on diff erent
line show the estimate?
-5.96 - (-6.83)
calculators, for
7
example,
,
≈ -6 - (-7)
+ -
−6
≈ -6 + 7
+/-
or
(-)
. It
is not the subtraction
≈ 1
−6
−5
−4
−3
−2
−1
+1
0
key,
-
. Experiment
Method 1: Use Paper and Pencil
with calculations
involving negative
Calculate.
Why is subtracting -6.83
signs on your
-5.96 - (-6.83) = -5.96 + 6.83
the same as adding its
calculator.
opposite, 6.83?
Determine 6.83 + (-5.96).
6.83 + (-5.96)
Why is -5.96 + 6.83 the
= 6.83 - 5.96
same as 6.83 + (-5.96)?
= 0.87
So, -5.96 - (-6.83) = 0.87.
Is the calculated answer
reasonable? How do you
know?
Method 2: Use a Calculator
Calculate. C 5.96 + -
- 6.83 + -
= 0.87
56
MHR • Chapter 2
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