Let S be the sequence of consecutive odd integers from 1 to 99.

Question

Let S be the sequence of consecutive odd integers from 1 to 99. Sequence T is obtained from S by removing the integer 3 and then removing every 3rd integer after 3. Sequence V is obtained from T by removing the integer 7 and then removing every 7th integer after 7. Which of the following integers is in V?

A. 9
B. 15
C. 21
D. 23
E. 29

A. 9
B. 15
C. 21
D. 23
E. 29

gmatophobia · Answer

As the number of terms is few, we can write the terms and check.

Set S = {1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31 .. }

Sequence T is obtained from S by removing the integer 3 and then removing every 3rd integer after 3

Inference : Multiples of three from set S is removed (hence option A, B and C are not possible)

Set S = {1,   3  , 5, 7,   9  , 11, 13,   15  , 17, 19,   21  , 23, 25,   27  , 29, 31 .. }

Sequence V is obtained from T by removing the integer 7 and then removing every 7th integer after 7

Remove 7 and then count 7 to the right in the remaining numbers.

29 gets removed & 23 remains.

Option D

sumit99kr · Answer

Multiples of 3 are removed in 1st operation, hence 9,15,21 cannot be the answer.

In 2nd operation 7,14,22 and 29 are removed.

The only answer left is 23.

Hence D is the correct choice.

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vektr · Answer

I have a doubt: 
S= (1,2,3,4,5,6,7,8,9,10,........,98,99)

For T, we will remove 3 and every 3rd integer afterwards from  S. 
=> T=(1,2,4,5,7,8,10,11,13,14,16,17,19,20,22,23,25,26,28,29,31.....97,98)

For V, we will remove 7 and 7th integer from  T (and not S) 
=> V= (1,2,4,5,8,10,11,13,14,16,19,20,22,23,25,26,29,31.....97,98)

Since we will remove 7th digit after 7 from T, both 23 and 29 would have to be part of set.
What am I getting wrong here?

Bunuel

Bunuel · Answer

Check below:
Let S be the sequence of consecutive   odd   integers from 1 to 99

Eipreel · Answer

Hi, could you kindly explain further why 29 is not the correct answer since we are removing the 7th integer after 7 which is 29 and not 23 to make up the set V or am I missing something here?

vektr · Answer

We are  removing  7th digit after 7. So as 29 gets removed, we have 23 in the set.

The question asks, "which of these integers will be part of V".

Eipreel · Answer

Well understood now thank you.

Let S be the sequence of consecutive odd integers from 1 to 99.

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GMAT Problem Solving (PS) Questions

Let S be the sequence of consecutive odd integers from 1 to 99.

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

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