This is an interesting counting methods question that combines a very basic rule of test of divisibility of number by 3. Question How many six digit positive integers comprising only the digits 1 and 2 can be formed such that the number is divisible by 3? 3 20 22 38 360 Correct Answer Choice C. 22 such numbers can be formed. Video Explanation Explanatory … [Read more...] about Permutation of Digits & Divisibility
GMAT Quant Theory & Practice Questions
Descriptive statistics – Standard Deviation
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