If m is the arithmetic mean (average) of 4 integers a, b, c, and d and s is the standard deviation of the 4 integers and s = , then is s > 0?(1) m > a(2) a + b + c + d = 0Solution:s will be zero only in two instances: (i) when all the elements in the set are the same, or (ii) the set contains only one element, which in this case is not possible. So, we need to check whether a, … [Read more...] about Descriptive statistics – Standard Deviation
Equations – roots and powers
How many roots does x6 –12x4 + 32x2 = 0 have?(A) 1(B) 3(C) 4(D) 5(E) 2Solution:x^6 –12(x^4) + 32(x^2) = x^2 (x^4 – 12x^2 + 32) = x^2 (x^2 – 4)(x^2 – 8)The roots are 0, ±2, and ±2√2: a total of 5.Please remember that ‘0’ is also a root.The correct answer is D … [Read more...] about Equations – roots and powers
Descriptive Statistics, Prime Numbers, Progression
This GMAT practice question tests your understanding of 3 topics. The core topic tested is Descriptive Statistics. Basic understanding of Prime Numbers and Progressions is needed to solve this question. Question The ages of three friends are prime numbers. The sum of the ages is less than 51. If the ages are in Arithmetic Progression (AP) and if at least one of the ages is … [Read more...] about Descriptive Statistics, Prime Numbers, Progression
GMAT Number Properties DS question
Number Properties is an often tested area as far as Data Sufficiency is concerned. Here is an interesting question. Question Is the two digit positive integer P a prime number? 1) P + 2 and P – 2 are prime. 2) P – 4 and P + 4 are prime. Statement (1): P + 2 and P – 2 are prime. One out of 3 consecutive odd integers, (P - 2), P, and (P + 2) will definitely be a … [Read more...] about GMAT Number Properties DS question
GMAT Statistics Practice – Median
Descriptive Statistics that includes mean, weighted mean, median, standard deviation and range is a GMAT favorite. At times it becomes "virulent" in its data sufficiency avatar.Here is a medium difficulty DS question from Descriptive Statistics:DirectionsThis data sufficiency problem consists of a question and two statements, labeled (1) and (2), in which certain data are … [Read more...] about GMAT Statistics Practice – Median