Math 7 Ratios and Proportions
proportions in graphs
1. Straight line (linear) 2. Goes through origin
how to find equivalent ratios
1. divide each fraction and see which ones are equal as decimals OR 2. Scale up or scale down OR 3. use cross products to see if they are equal
solve a word problem with proportions
1. read the problem carefully 2. set up a proportion carefully- lining up like units and making the unknown x 3. use cross products to write and solve an equation to find your missing infomation
How to solve a proportion with a missing value
1. use cross products to write and solve an equation OR 2. scale up or scale down
find the missing side of a similar figure
1. write a proportion, making sure to line up information correctly 2. use cross products to write and solve and equation for the missing side OR 1. Scale up or scale down
Use a proportion to solve a scale problem with missing information
1. write a proprotion (using the scale as the first rate), making sure to line up information correctly 2. use cross products to write and solve and equation for the missing information OR 1. Scale up or down if given a scale with 1
Multiply Mixed Numbers
Change them into improper Fractions, then use the rules for Multiplying Fractions
ratio
a comparison of two quantities using division
unit rate
a rate that has a denominator of 1
rate
a ratio that compares two quantities measured in different units
Perimeter of a rectangle
add all sides together (remember there are 4 sides)
proportion
an equation that states that two ratios are equal to each other
scaling up
creating an equivalent ratio by multiplying the top and bottom of a fraction by the same number
how to calculate best buy
divide price by number of both items and compare to see which unit rate is lower
how to calculate a unit rate
divide the numerator by the denominator
proportions in tables
divide y/x and see if they are all the same
perimeter of a rectangle under a scale factor
multiplied by the scale factor
area of a rectangle under a scale factor
multiplied by the scale factor squared
divide fractions
multiply by the reciprocal (keep, change, flip)
equivalent Ratios
ratios that have the same value
constant of proportionality
the constant ratio between two quantities, found by dividing y by x
y = kx
the formula used for proportional relationships, where k = the constant rate (COP)
( 1 , r )
the ordered pair for unit rate
cross products
the product of numbers on the diagonal when comparing two ratios are equal
describe a point on a graph based on the situation
use the labels to identify which each point refers to Ex. (1 , 30) = 1 hour for 30 miles or 30 miles per hour
non-proportional
when two quantities DO NOT have a constant rate or COP
proportional
when two quantities have a constant rate or COP
origin
( 0 , 0 )
multiply fractions
Multiply the tops, then multiply the bottoms, always reduce your answer
Divide Mixed Numbers
change into improper fractions, then multiply by the reciprocal (keep, change, flip)
scaling down
creating an equivalent ratio by dividing the top and bottom of a fraction by the same number
area of a rectangle
A=lw units are squared
