Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A necklace is made by stringing N individual beads together [#permalink]
18 Jan 2008, 10:14

1

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

100% (00:00) correct
0% (00:00) wrong based on 3 sessions

A necklace is made by stringing N individual beads together in the repeating pattern red bead, green bead, white bead, blue bead, and yellow bead. If the necklace design begin with a red bead and ends with a white bead, then N could equal

Re: PS - probability [#permalink]
18 Jan 2008, 11:35

Here's how the necklace looks when it is strung:

RED-GREEN-WHITE-BLUE-YELLOW

We know that the length of the pattern is 5 beads (shown above). The necklace begins at the red bead and then ends in a white bead. The shortest necklace we could have would be RED-GREEN-WHITE, which would only be 3 beads and then fit the bill. The next shortest necklace we could have would be when the pattern of 5 beads has been repeated again. In other words (3+5=8 beads) In this case the pattern would loop once (5 beads), then start RED(6)-GREEN(7)-WHITE(8).

The pattern that emerges here is that the number of beads will be in this list:

3 3+5 = 8 3+5+5 = 13 3+5+5+5 = 18 etc

Any easier way of writing this pattern would be to say that the number of beads must be divisible by 5 with 3 left over. or, when the number is divided by 5 it has a remainder of 3. Then we move onto our choices:

an even shorter method would be to realize that the number must end in 3 or 8 because multiples of 5 end in 0 or 5. Thus, the only choice that ends in 3 or 8 would be our answer!

Re: PS - probability [#permalink]
18 Jan 2008, 19:26

walker wrote:

E

20-sec way.

we should find the reminder of n divisible by 5

red bead - 1 green bead - 2 white bead - 3 blue bead - 4 yellow bead - 0

only 68 has reminder 3.

Walker, why it is not multiple of 8? I reason that it is multiple of 8 and I choose A and B, but bewteen A and B I can not decide which one? keke _________________