Each signal that a certain ship can make is comprised of 3 different

Question

Each signal that a certain ship can make is comprised of 3 different flags hanging vertically in a particular order. How many unique signals can be made by using 4 different flags?

A. 10
B. 12
C. 20
D. 24
E. 36

PS06380

gameCode · Accepted Answer

I would go for D and for following reasons.

A signal can be made using 3 flags. We have total of 4 , so 3 can be chosen out of 4 in 4C3 = 4C1 = 4 ways

The three flags can be arranged in 3 ! ways to make a unique combination. Hence 4 * 3! = 24 ways.

scthakur · Answer

Another way to look at it.

This is a permutation problem and hence answer will be 4P3 = 24.

selvae · Answer

D 4! i guess it should not be so simple :-)

. may be i am wrong.

ngotuan · Answer

my ans is D but it's not 4!
let's assume the signal is ABC
so A has 4 cases
 B has 3 cases
 C has 2 cases
so there are 4x3x2=24

rhine29388 · Answer

Consider a flagpole with 3 vertical slots for flags 
As we have to select different flags we can do as follows
topmost flag can be paced in 4 ways
middle flag can be placed in 3 ways
bottom most flag can be placed in 2 ways
(order doesn't matter the selection matters)
Total ways = 4 * 3 * 2 = 24 ways
correct answer - D

ydmuley · Answer

As the order matters:

4 (First Flag) * 3 (Second Flag) * 2 (Third Flag)

24

Hence, Answer is D

Business Analyst · Answer

Can anyone please share any theory topic related to this problem I am not getting it
TIA

ydmuley · Answer

Here you will find all the theory topics explained very well. https://gmatclub.com/forum/gmat-math-bo ... 30609.html

TimeTraveller · Answer

One signal has 3 different flags. No. of unique signals that can be made = 3*2*1 = 6.
No. of ways of choosing 3 flags from 4 flags = 4c3 = 4.

No. of signals that can be made = 24. Ans - D.

JeffTargetTestPrep · Answer

The number of unique signals is 4P3 = 4 x 3 x 2 = 24.

Answer: D

MathRevolution · Answer

Flags available : 4
Signal has: 3 flags

For first flag: 4 choices.
Second flag:3 choices
Third flag: 2 choices

Overall: 4 * 3 * 2 = 24 ways

Answer D

AbY700 · Answer

A (n,m) = n!/ (n-m)! 
A (4, 3) = 4!/ (4-3) ! = 4! = 24
Answer is D

CEdward · Answer

Combinations + Permutations.

4C3 x 3! = 4 x 6 = 24.

Answer is D.

DanTheGMATMan · Answer

Straightfoward permutation:

https://www.youtube.com/watch?v=ssuQB8tDfWg

bumpbot · Answer

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Each signal that a certain ship can make is comprised of 3 different

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Each signal that a certain ship can make is comprised of 3 different

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