Decimal Form Of Rational Numbers Worksheet - Chapter 2.2, Mathlink 9, Mcgraw-Hill Ryerson School Page 4
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8Example 3:
Apply Operations With Rational Numbers in
Decimal Form
On Saturday, the temperature
at the Blood Reserve near
Stand Off, Alberta decreased
by 1.2 °C/h for 3.5 h. It then
decreased by 0.9 °C/h
for 1.5 h.
What was the total decrease
a)
in temperature?
What was the average rate of decrease in temperature?
b)
Solution
Why are the time
The time periods can be represented by 3.5 and 1.5. The rates
a)
periods represented
of temperature decrease can be represented by -1.2 and -0.9.
by positive rational
numbers?
Why are the rates of
Method 1: Calculate in Stages
temperature decrease
You can represent the temperature decrease in
represented by
the fi rst 3.5 h by 3.5 × (-1.2) = -4.2.
negative rational
numbers?
You can represent the temperature decrease in
4 × (-1) = -4
the last 1.5 h by 1.5 × (-0.9) = -1.35.
1.5 × (-1) = -1.5
Add to determine the total temperature decrease.
-4 + (-1.5) = -5.5
-4.2 + (-1.35) = -5.55
The total decrease in temperature was 5.55 °C.
Method 2: Evaluate One Expression
The total temperature decrease
can be represented by
3.5 × (-1.2) + 1.5 × (-0.9).
4 × (-1) + 1.5 × (-1) = -5.5
Evaluate this expression, using
Literacy Link
the order of operations.
3.5 × (-1.2) + 1.5 × (-0.9)
Order of Operations
= -4.2 + (-1.35)
• Perform operations
inside parentheses
= -5.55
fi rst.
You can also use a calculator.
• Multiply and divide
C 3.5 × 1.2 + -
+ 1.5 × 0.9 + -
= -5.55
in order from left to
right.
The total decrease in temperature was 5.55 °C.
• Add and subtract in
order from left to
The average rate of decrease in temperature is the total decrease
b)
right.
divided by the total number of hours.
The total number of hours is 3.5 + 1.5 = 5.
-5.55
______
= -1.11
-5 ÷ 5 = -1
5
The average rate of decrease in temperature was 1.11 °C/h.
58
MHR • Chapter 2
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