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24 Cards in this Set
- Front
- Back
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A and B are both two digit numbers. If A and B contain the same digits but in reverse order, what integer must be a factor of (A + B)?
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A + B = 10 x + y + 10y + x = 11x + 11y = 11(x+y) So, 11 must be a factor of A + B.
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When a question asks you about "digits", think
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100h + 10t + u etc….
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What is the Last Digit Shortcut? What is the units digit of 4^2 * 9^2 * 4^3?
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Only pay attention to the last digit of every intermediat product. 0.
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What is the Heavy Division Shortcut?
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Only pay attention to first few digits…and divide.
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For proper fractions between 0 and 1:As the NUMERATOR goes up, the fraction __
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INCREASES
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For proper fractions between 0 and 1:As the DENOMINATOR goes up, the fraction __
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DECREASES
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Increasing BOTH the numerator and the denominator by THE SAME VALUE brings the fraction_________
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closer to 1…
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When you have complex ractions, you can NEVER split the ______
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DENOMINATOR
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What is a Benchmark Value?
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Simple fractions with which you are already familiar.
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Percent change _____
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Change / Original * 100.
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Simple Interest equation:
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Principle * Rate * Time
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Compound Interest Equation:
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P(1 + r/n) ^ (nt) P = Principle. R = rate. N - number of times per year. T = # of yrs
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Chemical Mixture Problems: 500 ml solution is 20% alcohol. If 100 ml of water is added, what is the new concentration of alcohol?
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Alcohol 100 ml 20% Alcohol 100 ml Water 400 ml 80% Water 500 ml Total 500 ml 100% Total 600 ml 100% 100 / 600 => 16.6%
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1/100 => Decimal, Percent
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.01, 1%
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1/50 => Decimal, Percent
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.02, 2%
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1/25 => Decimal, Percent
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.04, 4%
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1/20 => Decimal, Percent
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.05, 5%
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1/10 => Decimal, Percent
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.1, 10%
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1/8 => Decimal, Percent
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0.125, 12.5%
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1/6 => Decimal, Percent
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.1666, 16.6%
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1/5 => Decimal, Percent
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.2, 20%
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1/4 => Decimal, Percent
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0.25, 25%
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The key to DS problems dealing with FDP's is to
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rephrase questions / statements into equations in order to keep track of what you know and what you need to know…
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DS: If a brokerage firm charged a commission of 2% of the total dollar amount of a certain trade, what was the total dollar amount of that trade? I. The dollar amount of the trade minus the brokerage firm's commission was $88,000. II. The brokerage firm's commission decreased the profit earned on the trade by 20%.
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d = total dollar amount of trade. Let c - brokerage firm's commission -> c = .02d Test each statement, writing equations to represent information. If the info in the statement can be combined w/ the info in the question to ield a single equationwith the single variable d, then the statement is sufficient: I.: d - c = $88,000 Rephrase: d - .02d = 88,000. Sufficient. II. P = profit before commission. p - c = .80p. We do not know p, the amount of profit before commission, so you cannot solve for c, the brokerage firm's commission. Not Sufficient.
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