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