STRATEGY: Since you need to find a total and you are given two different
items (gallons and hours), you multiply.
IMPLEMENTATION: 0.62.6¼1.56 gallons.
EVALUATION: You can check your answer using estimation. You use
about one half of a gallon per hour. In two hours you would use about one
gallon and another half of a gallon for the last half hour, so you would use
approximately one and one half gallons. This is close to 1.56 gallons since
one and one half is 1.5.
EXAMPLE:Before Harry left on a trip, his odometer read 46351.6. After the
trip, the odometer reading was 47172.9. How long was the trip?
SOLUTION:
GOAL: You are being asked to find the distance the automobile traveled.
STRATEGY: In order to find the distance, you need to subtract the two
odometer readings.
IMPLEMENTATION: 47,172.946,351.6¼821.3 miles.
EVALUATION: Estimate the answer by rounding 47,172.9 to 47,000
and 46,351.6 to 46,000; then subtract 47,00046,000¼1000 miles. Since
821.3 is close to 1000, the answer is probably correct.
Sometimes, a word problem requires two or more steps. In this situation,
you still follow the suggestions given in Lesson 2 to determine the operations.
EXAMPLE:Find the total cost of 6 electric keyboards at $149.97 each
and 3 digital drums at $69.97 each.
SOLUTION:
GOAL: You are being asked to find the total cost of 2 different items: 6 of
one item and 3 of another item.
STRATEGY: Use multiplication to find the total cost of the keyboards and
the digital drums, and then add the answers.
LESSON 3 Using Decimals 15