-
Proportions
- If the problem has 3 numbers given and ask for a 4th this may be a
clue that the problem is a proportion problem.
- It must also have a ratio.
- Make certain the units are the same
- Below is an example of the above.
- Example:
- Grandma can ride the
24 miles to
Blackfoot in two
hours on her bike. If she rides at the same rate, how long will it take
her to ride her bike the 36
miles to Rexburg?
- Step one:
How many numbers are given? There
are 3 and it asks for a fourth--
- Step two:
Is a ratio given? 24 miles to 2
hours ----24 : 2
- Step three:
set up the problem with two lines,
labels and an equals.
miles 24 = 36
- hours 2 x
.
- Step four:
Fill in numbers. Put the given
ratio on one side of the equal sign. Put the other piece of
information on the same level as its label. Put an “x” in the empty
space.
- Step five
: Solve the proportion. Cross
multiply -- 24x = 2(36) 24x = 72 x = 3 hours
-
Divide each side24 24