Exam 7: Computing With Fractions
One meaning of 16/19 ÷ 25/17 is, "How many 25/17 of 1 are in 16/19 of 25/17?"
False
Using a rectangular region as the unit, illustrate each of the following.
A)
B)
C)
A) The expected way is to start with 2/3 of a rectangular region shaded. Cut it with marks perpendicular to the marks for thirds to give slivers that are fifths (and small boxes that are fifteenths), turning the 2/3 into 10/15. Notice that, in order to add another 4/5, we need 12/15, yet there are only 5/15 left in the first box. A duplicate of the first box needs to be made, so the other 7/15 can be shaded. An additional 4/5 would entail four slivers or 12 small boxes. Since there are only five small boxes left, seven small boxes, or 7/15, of another whole is needed.
B) This is similar to part A, except that each addend is more than one whole. There are 2 9/10 when all the work is done.
C) The easiest way is to recognize that 10/8 = 5/4 = 1 1/4, but that may not be regarded as fair. Show 10/8 with parallel cutting marks and shading on the two rectangular regions. That should show that 1/2 is 4/8, which can then be crossed out from the 10/8.
Following is an example of a child's work. You are to study the work and then judge the student's understanding.
?
Rona was asked to subtract
from
. Her work is shown below.
Rona's work: 4=3 1 ?
A) Is Rona's work correct or incorrect?
B) If the work is incorrect, please explain why.
A) Incorrect
B) In changing a 1 from the 4 into eighths, Rona did the usual base-ten place value, borrowing 10 rather than the correct 8/8 + 1/8.
Division involving only positive numbers always gives a smaller answer than the number being divided.
Which point of A-E would BEST locate the point for n ÷ 0.89 on the number line (n is positive)? 

How many portions of 2/3 a pound can be obtained from 30 pounds?
Karen and Sara go for a bike ride. Karen biked for Hours, which was 2/3 as many hours as Sara biked. How many hours did Sara bike?
What calculation would solve this story problem?
George had 4/5 of a pie. He ate 2/3 of what he had. What part of a whole pie did he eat?
The stagecoach robbers have a 12-mile head start on the sheriff's posse. But the sheriff's posse has faster horses, so the posse catches up by 3/4 of a mile every hour. How many hours will it take the posse to catch the robbers? Show your work.
Which location on the number line indicated by the letter P, Q, R, S T, U, or W represents each of the following?
A) 1/2 × 2
B) 5/8 of 1/2
C) 3/4 of 2/3
D) 1 ÷ 2/3
E) 1/4 ÷ 1/3

Finish the following story problem so that your question could be answered by the calculation 18 ÷1/2.
You buy 18 muffins for an after-school faculty meeting …
If two numbers are multiplied, their product is greater than (or equal to) each number.
After the family had gone 140 miles, the children asked, "Are we getting close?" The driver said, "We've gone only 2/7 of the way." How far did the family still have to go?
One meaning of 45/59 ÷ 35/17 is, "How many 35/17of 1 are in 45/59 of 1?"
One day, Joe's old car used 5/8 of a quart of oil. The next day, it used only 2/3 as much oil. How many quarts of oil did the car use on the second day? Which computation will answer the question?
Three-fourths of seven ones is the same amount as seven 3/4 of one.
Is one meaning of 1/4 × 1/3 the following: How many 1s is 1/4 of 1/3 of 1? If it is one meaning, how much of a 1 or how many 1s?
A) On the number line below, show approximately where 4/7 + 1/2 would be using number sense. Label it
B) On the same number line, show approximately where 4/7 - 1/2 would be, using number sense. Label it b.


Donny is asked to solve the following problem: If cheese is $1.89 per pound, how much does 0.67 pounds cost? Which computation will answer the question?
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