Planet 1 Flashcards
Word problems are a good opportunity to…
Backsolve
When a word problem includes variables in the answer choices…
Pick Numbers
Mistakes tend to happen on word problems when…
You solve for the wrong thing (Liters of petrol in the tank vs liters of petrol used)
In word problems, how to assign and treat variables…
Assign for boy as B, not X. Underline what you’re solving for.
Work =
Rate x Time
Distance =
Rate x Time
Rate =
Work / Time
Rate =
Distance / Time
Rates are…
Additive. If two working together, you can combine them for a combined rate.
Multiple rates and changing conditions?
Reset when conditions change
Convert time to?
Rates. Machine 1 can complete the job in 5 hours — 1/5. Remember, a rate is always the inverse of the time for one unit of work.
Collision problems (two people/cars/etc meeting)
Combine their rates
Catching up problems
Subtract their rates
Rate and time are…
Inversely proportional
When given a formula as an answer…
Try number picking
When to use venn diagram?
When you see “both” or “neither” in a word problem, suggesting you are working with overlapping sets
Write out a venn diagram and both equations
A + B - Both + Neither = Total; A only + B only + Both + Neither = Total
When to use matrix boxes?
When you have sets of complimentary information - red vs not red, sold vs not sold
Matrix beware…
When entering percent or fraction information that you are taking it of the right item
Triple venn formula
A + B + C - AB Only - BC Only - AC Only - 2xall 3 + Neither = Total
When matrix boxes provide percent or fraction data, its a good idea to…
Pick your own numbers
Two equations, two variables?
Enough to solve in DS
Remember, if a statement does not say “ONLY” in an overlapping problem…
It does not mean only
Min/Max problems…3 questions…
1) Numbers have to be positive? 2) Numbers repeat? 3) Numbers have to be integers?
