direct proportions developed by ivan seneviratne
TRANSCRIPT
Direct Proportions
Developed byIvan Seneviratne
ProportionsProportions
A proportion is an equation that states the equality of two rates or ratios. In other words, a proportion is an equation with a ratio on each side.
Example3/4=6/8
Two quantities are in direct proportion when they increase or decrease in the same ratio. The cross-products method, can be used to solve a proportion problem.
The Cross-Products MethodThe Cross-Products Method
(read “a is to b as c is to d”)
Means-extremes property:
Product of the means is equal to the product of the extremes where a, d are the extremes and b, c are the means.
cbdad
c
b
a
ProblemJustin was a great chef. He worked at a fabulous restaurant in Paris. His customers ate snails to snake skins at a ratio of 3 to 7. If they ate 40 snake skins, how many snails did they eat?
Uncompleted
Situation
Complete Situation
Snails
Snake
3
7
Uncompleted
Situation
Complete Situation
Snails
42
3
7
Cross Multiply
Snails 3 7
42
They ate 18 snails
1. Jonathan became a great golf player. He won 7 games to 4 that he lost. If he won a total of 42 games, how many did he lose?
2. Cecil talked 18 times to the 12 times that John talked. If Cecil talked a total of 72 times, how many times did John talk?
3. Felix cycled 4 km in 24 min. At this rate, how long does he take to cycle 10 km?
Your Turn
24 games
48 times
60 min
This presentation is developed by Ivan Seneviratne © 2008 purely for personal [email protected]