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Math, A Practical Art

My Math Cheat Sheet

• Frequency: the number of data values in a class
• Relative: frequencies divided by total data values
• Percentage: relative x 100
• Frequency polygon: line graph; pie chart
• Mean: sum of all values / total # of values OR for each (add) freq(value) / total freq of values
• Median: the middle number of the set, or split diff
• Mode: occurs most frequent, only bi-modal or no mode
• Range: subtract the lowest from highest in data set
• Standard Deviation: the sq. root of [{for each} (data value â€“ mean)2 / number of data values
• Draw the bell curve. Make sure to account for the other half in the answer (50% above or below)
• Std Dev. Grouped: the sq. root of [{for each} freq (midpoint â€“ mean)2 / total frequencies]
• Normal Distribution: z = (data value â€“ mean) / standard deviation
• Margin of Error: Margin = z value / 2 (sq. root of population) [confidence/2 then look up area.]
• Regression Line: Table of values: x  |  y  |  x2 |  xy, and sum of each column.    where âˆ‘ = sum   n = # of points
y = a + bx                  b = [nâˆ‘(xy) â€“ (âˆ‘x)( âˆ‘y)] / [nâˆ‘ (x2) â€“ (âˆ‘x)2]                 a = [âˆ‘y â€“ b(âˆ‘x)] / n
• Percent: out of 100
• Percent to Decimal: Move decimal 2 & drop %
• Fraction <-> Decimal key
• Retail: Price + Markup
• % Inc or Dec: amount of inc or decrease / base starting amt (use the inverse of the percent if needed)
• Simple Interest rate:  I = Prt (principal x rate x time)
• Amount Simple Int. Acct: A = P(1 + rt)
• Compound/Nominal rate: A = P(1+r)n [r = periodic interest rate = (annual rate / periods per yr)  and n= number of time periods = (years x periods per yr)]
• Compound interest over time. Calculate each period. Then add all.
Make sure n & r are correct! Make sure time is all in the same units (years vs. months)! Don’t remove negative w/1.
• Effective Interest Rate: reff = (1 + r)n â€“ 1              [r = periodic interest rate and n = number of periods per year)
• To get rid of exponent: move n outside number, LN both side                 512n = 25 â€¦ 12n(ln5) = (ln25)
• Annuity (fixed deposit) r = periodic rate    n = # of deposits
• Amount in Annuity = PMT [ ((1+r)n â€“ 1) / r]
• Loans formula r = periodic rate    n = # of payments
• Loan = PMT [(1- (1 + r) â€“n ) / r]
Standard

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