1. 3.9 Continued….Word Problems Involving Proportions
How do you know when to use proportions?
When you see a comparison of units

2. How to tackle word problems
Set up a table
Set up a proportion
Cross multiply
Set products equal
Solve for x
Put units on answer
units
Fill in the blank

3. 1. ) A car travels 150 km on 12 l of gasoline
1.) A car travels 150 km on 12 l of gasoline. How many liters of gasoline are needed to travel 500 km?
Liters of Gasoline 12 x KM
150
500
12(500) = 150 (x)
6000 =150x
40 Liters of Gasoline =x

4. 2. ) A watch loses 2 minutes every 15 hours
2.) A watch loses 2 minutes every 15 hours. How much time will it loose in 2 hours?
minutes 2 x
hours 15
15(x) = 2(2)
15x =4
X = of a minute

5. 3. ) On a certain map, 2 inches represents 5 miles
3.) On a certain map, 2 inches represents 5 miles. 9 inches represent how many miles?
inches 2 9
miles 5 x
2(X) = 5(9)
2x =45
X = 45/2 or 22.5 miles

6. 4 64 5 x 4x = 320 X = 80 shovels of gravel
4.) 4 shovels of sand are used for every 5 shovels of gravel in making concrete. How much gravel is needed for 64 shovels of sand?
Shovels of sand 4 64
Shovels of gravel 5 x
4(x) = 5 (64)
4x = 320
X = 80 shovels of gravel

7. Assignment Page 150 ( 26-38) even you do not have to write down the entire word problem but you do need the table, the proportion and work