GMAT Math Ultimate Well Solved Questions and Answers 100% out of 100% Graded A+

GMAT Math Ultimate Well Solved Questions and Answers 100% out of 100% Graded A+ Common Factors - CORRECT ANSWER-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 - CORRECT ANSWER-Gross profit = Selling Price - Cost Combined Events - CORRECT ANSWER-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 - CORRECT ANSWER-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 - CORRECT ANSWER-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 - CORRECT ANSWER-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 - CORRECT ANSWER-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 - CORRECT ANSWER-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 - CORRECT ANSWER-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) - CORRECT ANSWER-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) - CORRECT ANSWER-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) - CORRECT ANSWER-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 - CORRECT ANSWER-The number of ways to arrange n distinct objects along a fixed circle is: (n - 1)! Slope of a Line - CORRECT ANSWER-y = mx + b m = slope = (difference in y coordinates)/(difference in x coordinates) = (y2 - y1)/(x2-x1) 30-60-90 Triangle - CORRECT ANSWER-30-60-90 x (shorter leg), x(sqrt 3) (longer leg), 2x (hypotenuse) 45-45-90 Triangle - CORRECT ANSWER-45-45-90 x (shorter legs), x(sqrt 2) (hypotenuse) Common Right Triangles - CORRECT ANSWER-3-4-5 or 6-8-10 or 9-12-15 5-12-13 Number Added or Deleted - CORRECT ANSWER-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 - CORRECT ANSWER-Odd numbers have only odd factors Quadratic Formula - CORRECT ANSWER-To find roots of quadratic equation: ax^2+ bx + c = 0 x = [−b ± √(b^2 − 4ac)]/2a Discriminant - CORRECT ANSWER-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 - CORRECT ANSWER-(x^r)(y^r)=(xy)^r (3^3)(4^3)=12^3 = 1728 Prime Factorization: Greatest Common Factor (GCF) - CORRECT ANSWER-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) - CORRECT ANSWER-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 Check for Prime - CORRECT ANSWER-1. Pick a number n. 2. Start with the least prime number, 2. See if 2 is a factor of your number. If it is, your number is not prime. 3. If 2 is not a factor, check to see if the next prime, 3, is a factor. If it is, your number is not prime. 4. Keep trying the next prime number until you reach one that is a factor (in which case n is not prime), or you reach a prime number that is *equal to or greater than the square root of n.* 5. If you have not found a number less than or equal to the square root of n, you can be sure that your number is prime. Ex: the number n=19 has a square root of ~4.35. Test 2, 3, 4 -- you know 19 is prime because none of them are factors, and any other factor would be greater than sqrt(19). Rate x Time = Distance (rt = d) - CORRECT ANSWER-For a fixed distance, the average speed is inversely related to the amount of time required to make the trip. Ex: Since Mieko's average speed was 3/4 of Chan's, her time was 4/3 as long. (3/4)r(4/3)t = d Factoring Exponents - CORRECT ANSWER-(5^k)−(5^k−1) (5^k)-(1/5)(5^k) (5^k)(1 - 1/5) (4/5)(5^k) Squaring Fractions - CORRECT ANSWER-When positive fractions between 0 and 1 are squared, they get smaller. Ex: (1/2)^2 = 1/4 Approximations of Common Square Roots - CORRECT ANSWER-Square root of 2 = 1.4 Square root of 3 = 1.7 Square root of 5 = 2.25 Inscribed Angle, Minor Arc - CORRECT ANSWER-An inscribed angle = two chords that have a vertex on the circle Inscribed angle with one chord as diameter = 35 degrees Minor arc = 2 x inscribed angle = 70 degrees Area of Trapezoid - CORRECT ANSWER-A = (sum of bases)(height)/2 A = {[(b1 + b2)/2](height)}/2 Area of a Rhombus - CORRECT ANSWER-A = bh OR A = [(d1)(d2)]/2 Compound Interest Formula - Compounding Annually - CORRECT ANSWER-To compound annually: P = principal r = rate of interest (in decimal form) y = number of years New value = P (1 + r)^y Compound Interest Formula - Compounding More Than Annually - CORRECT ANSWER-To compound multiple times per year: P = principal r = rate of interest (in decimal form) y = number of years n = number of times per year (i.e., compounded every 3 months would be n = 4) FV = P (1 + r/n)^ny Interest Problem: If $10,000 is invested at 10% annual interest, compounded semi-annually, what is the balance after 1 year? - CORRECT ANSWER-P = 10,000 r = .10 y = 1 n = 2 FV = P (1 + r/n)^ny FV = 10,000 (1 + .1/2)^(2)(1) FV = 10,000 (1.1025)^2 = 10,000 (1.1025) = $11,025