GMAT Math Ultimate Test| Verified

Common Factors - Break down both numbers to their prime factors to see what factors they have in common. Multiply all combinations of shared prime factors to find all common factors. Gross Profit - Gross profit = Selling Price - Cost Combined Events - For events E and F: • not E = P(not E) = 1 - P(E) • E or F = P(E or F) = P(E) + P(F) - P(E and F) • E and F = P(E and F) = P(E)P(F) Multiplication Principle - The number of ways independent events can occur together can be determined by multiplying together the number of possible outcomes for each event. 1st Rule of Probability: Likelihood of A - Basic rule: The probability of event A occurring is the number of outcomes that result in A divided by the total number of possible outcomes. 2nd Rule of Probability: Complementary events - Complementary Events: The probability of an event occurring plus the probability of the event not occurring = 1. P(E) = 1 - P(not E) 3rd Rule of Probability: Conditional Probability - Conditional Probability: The probability of event A AND event B occurring is the probability of event A times the probability of event B, given that A has already occurred. P(A and B) = P(A) × P(B|A) 4th Rule of Probability: Probability of A OR B - The probability of event A OR event B occurring is: the probability of event A occurring *plus* the probability of event B occurring *minus* the probability of both events occurring. P(A or B) = P(A) + P(B) - P(A and B) Probability of Multiple Events - Rules: • A *and* B A *or* B • A *or* B Individual probabilities of A, B • P(A and B) = P(A) x P(B) ← "fewer options" • P(A or B) = P(A) + P(B) ← "more options" Indistinguishable Events (i.e., anagrams with repeating letters) - To find the number of distinct permutations of a set of items with indistinguishable ("repeat") items, divide the factorial of the items in the set by the product of the factorials of the number of indistinguishable elements. Example: How many ways can the letters in TRUST be arranged? (5!)/(2!) = 60 5! is the factorial of items in the set, 2! is the factorial of the number of repeat items ("T"s) Combinations (Order Does Not Matter) - nCr = n! / (r! (n - r)!) Where n is the total number of items in the set and r is the number of chosen items. Permutations (Order Does Matter) - nPr = n! / (n - r)! Where n is the total number of items in the set and r is the number of chosen items. Circular Permutations - The number of ways to arrange n distinct objects along a fixed circle is: (n - 1)! Slope of a Line - y = mx + b m = slope = (difference in y coordinates)/(difference in x coordinates) = (y2 - y1)/(x2-x1) 30-60-90 Triangle - 30-60-90 x (shorter leg), x(sqrt 3) (longer leg), 2x (hypotenuse) 45-45-90 Triangle - 45-45-90 x (shorter legs), x(sqrt 2) (hypotenuse) Common Right Triangles - 3-4-5 or 6-8-10 or 9-12-15 5-12-13 Number Added or Deleted - Use the mean to find number that was added or deleted. • Total = mean x (number of terms) • Number deleted = (original total) - (new total) • Number added = (new total) - (original total) Factors of Odd Numbers - Odd numbers have only odd factors Quadratic Formula - To find roots of quadratic equation: ax^2+ bx + c = 0 x = [−b ± √(b^2 − 4ac)]/2a Discriminant - Quadratic equation: ax^2+ bx + c = 0 Dicriminant = b^2 - 4ac If discriminiant 0, there are two roots (and two x-intercepts) If discriminant = 0, there is one root (and one x-intercept) If discriminant 0, there are no (real) roots Exponents - (x^r)(y^r)=(xy)^r (3^3)(4^3)=12^3 = 1728 Prime Factorization: Greatest Common Factor (GCF) - 1. Start by writing each number as product of its prime factors. 2. Write so that each new prime factor begins in same place. 3. Greatest Common Factor (GCF) is found by multiplying all factors appearing on BOTH lists. 60 = 2 x 2 x 3 x 5 72 = 2 x 2 x 2 x 3 x 3 GCF = 2 x 2 x 3 = 12 Prime Factorization: Lowest Common Multiple (LCM) - 1. Start by writing each number as product of its prime factors. 2. Write so that each new prime factor begins in same place. 3. Lowest common multiple found by multiplying all factors in EITHER list. 60 = 2 x 2 x 3 x 5 72 = 2 x 2 x 2 x 3 x 3 LCM = 2 x 2 x 2 x 3 x 3 x 5 = 360