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Ratio Box
Ratios are part-to-part relationships.
| M | W | Total |
-------------------------------|
Ratio       |  2 + 3 =  5     |
---------------x----x---------|
Multiplier |  7 = 7 =  7     |
-------------------------------|
Actual #  | 14 | 21 |  35   |
-------------------------------|
Ratios
The ratio of grape juice to orange juice is 2 to 3.
The ratio of grape juice to orange juice is 2:3.
The ratio of grape juice to orange juice is 2/3.
Proportions
1 hour         3 hours
---------  = ------------
60 min       180 mins

Match the units!
Average Pie
Average = (Total)/(# of things)

|-----------------------|
|        Total            |
|-----------------------|
|# of    | Average    |
|Things |                |
|-----------------------|
What is the Average of 200 to 400, inclusive?

Average = 300
The middle value between 200 and 400 is 300. For every integer above 300 there exists an integer below 300 that is the same distance away from 300. So, the average for this range of values is 300.

Official Guide 12, pg 46, #2.
Rates of Change
Rate = Dist/Time
Dist = (Rate)x(Time)

Rate = Work/Time
Work = (Rate)x(Time)

You can combine rates.

OG 12, PS, #80, p. 163

Sample Work Problem (click)
Median
Median is the middle number in a set after the set has been arranged in ascending order. If there is an even number of elements, the median is the average of the two middle numbers.

Remember to arrange in ASCENDING order before finding the median! Least to greatest.
Mode
Mode is the most frequently occuring number in a set.
Range
Range is the difference between the highest and lowest numbers.  Greatest minus the Least.  All the numbers in between are irrelevant for the range.

Also, Greatest = Range + Least
Standard Deviation
Standard Deviation (sd) also known as Normal Distribution. Draw a bell curve.

Mean goes in the middle of the bell curve.

2% - 14% - 34% - 34% - 14% - 2%.
Simultaneous Equations in Data Sufficiency
-Sometimes these are actual equations but simultaneous equations can also be word problems.
-Be wary of equations that are identical but just scaled up or down from the first equation.
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