4GMAT - GMAT Online Practice Test
 

GMAT Questions Mailing List - Y! Groups Algebra Arithmetic and Geometric Progressions Arithmetic Mean, Median, Mode, Deviation Inequalities Data Sufficiency Geometry Mensuration Number Systems Percentages Permutation and Combination, Probability Profit & Loss Quadratic Equations Ratio, Proportion, Variance Set Theory Simple & Compound Interest Speed, Time, Distance Work & Time, Pipes & Cisterns

Permutation and Combination - January 30, 2004

The GMAT Sample Math question for the day is from the topic Permutation and Combination.

Question
Ten coins are tossed simultaneously. In how many of the outcomes will the third coin turn up a head?

A. 210
B. 29
C. 3*28
D. 3*29
E. None of these

The correct choice is (B) and the correct answer is 29.

Explanatory Answer
When a coin is tossed once, there are two outcomes. It can turn up a head or a tail.

When 10 coins are tossed simultaneously, the total number of outcomes = 210

Out of these, if the third coin has to turn up a head, then the number of possibilities for the third coin is only 1 as the outcome is fixed as head.
Therefore, the remaining 9 coins can turn up either a head or a tail = 29
Copyright 2004-06 4GMAT.COM, Test Catalyst (India) Private Limited - all rights reserved
GMAT™ and GMAC™ are registered trademarks of the Graduate Management Admission Council™. The Graduate Management Admission Council™ does not endorse, nor is it affiliated in any way with the owner or any content of this web site.