Road (m) |
map (cm) |
500 |
4 |
R |
5 |
Here are three examples for you to try on your own. If you get stuck, click on the hint buttons. Following each example are samples of four multiple choice options.
Sarah is working on a project for her social studies class. She has to draw a scale map of her neighborhood. The road that she lives on is 500 meters long, and she has represented it with a 4 centimeter long line segment. A different road on her map is represented by a 5 centimeter long line segment. Write a proportional equation that would determine the actual length of the road that is modeled by the 5 centimeter line segment.
Interactive popup. Assistance may be required.Road (m) |
map (cm) |
500 |
4 |
R |
5 |
Interactive popup. Assistance may be required.
The constant of proportionality (unit rate) that
changes 500 m → 4 cm
will change R → 5 cm.
The same scale factor that changes 4 → 5,
will change 500 → R.
Interactive popup. Assistance may be required.
Depending on if you use the constant of
proportionality (unit rate) or scale factor, you
could get either one of these equations:
500 4 = R 5
Or
500 R = 4 5
Choose the correct answer for the problem.
Why wasn't my answer one of the four choices?
Interactive popup. Assistance may be required. Recall that, in order for the proportion to be correct, some common element must tie the numerators together. Another common element ties the denominators together.| 10 over 17 10 17 = 2 over L 2 L | 2 over L 2 L = 10 over 17 10 17 | 10 over 2 10 2 = 17 over L 17 L | 17 over L 17 L = 10 over 2 10 2 |
A work crew can dig 7 holes in 4 hours. If the crew maintains the same pace, how long would it take them to dig 9 holes?
Interactive popup. Assistance may be required.| Holes | Hours |
| 7 | 4 |
| 9 | T |
Interactive popup. Assistance may be required.
The constant of proportionality (unit rate) that changes
7 holes → 4 hours
will change 9 holes → time T.
Or
The same scale factor that changes 7 holes → 9 holes
will change 4 hours → time T.
Interactive popup. Assistance may be required.
Depending on if you use the constant of
proportionality (unit rate) or scale factor, you
could get either one of these equations:
7 4 = 9 T
Or
7 9 = 4 T
Choose the correct answer for the problem.
Three friends are working on a project together. The final project ends up being 15 pages long. Mark wrote 40% of the paper, Steve wrote 2 15 of the paper, and Jennifer wrote 7 pages. Who wrote the largest portion of the paper?
Interactive popup. Assistance may be required.| Mark | Steve | Jennifer | |
| portion | 40% |
2
15
|
|
| pages | 7 |
Interactive popup. Assistance may be required.
| Mark | Steve | Jennifer | |
| portion | 6 15 | 2 15 | 7 15 |
| pages | 6 | 2 | 7 |
Interactive popup. Assistance may be required.
Jennifer wrote the largest portion.
Choose the correct answer for the problem.