s.a.t. math testing tactics tactic 10: don’t do more than you have to
TRANSCRIPT
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S.A.T. Math Testing Tactics
Tactic 10: Don’t Do More Than You Have To
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Don’t Do More Than You Have To!
Look for shortcuts
Many problems have more than one correct way to obtain the right solution
Think: Quick, Efficient, Accurate
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Example 10.1
If , what is ?5(3 7) 20x 3 8x
First: Notice that there is a 3x in the given equation AND the expression we are evaluating.
This means we can solve for 3x instead of x. This will save time!
5(3 7) 20x
3 7 4x
3 11x
3 8x 11 83
3
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Example 10.2
If and , what is the average (arithmetic mean) of x and y?
7 3 17x y 3 7 19x y
First, what does the average of x and y look like?2
x y
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Ex 10.2 (continued)Next, since we have two equations, let’s try adding them together (Tactic 17):
7 3 17x y ( )3 7 19x y
10 10 36x y
10 10 36
10 10
x y
3.6x y
3.6
2 2
x y
1.82
x y
Average of x and y= 1.8
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Example 10.3If , what is the value of ?
5 13 31x 5 31x
Notice the equation and the expression both have a 5x
5 13 31x 5 18x
5 31x
18 31497
7
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In conclusion: EVERY SECOND IS PRECIOUS–
WORK SMARTER, NOT HARDER!
ALWAYS LOOK FOR SHORTCUTS!
Don’t find 20% and 30% separately if you can find 50% once.
Don’t find x if you really only need 5x.
Don’t find individual numbers if you only need their sum.
DON’T WASTE PRECIOUS TIME!