Each baby born at a certain hospital last week was either a single bir

Question

Each baby born at a certain hospital last week was either a single birth or one of a pair twins. If x is the number of babies born at the hospital last week, is x odd?

(1) There were 33 single births at the hospital last week 
(2) There were 3 pairs of twins born at the hospital last week

ID 10621

NoHalfMeasures · Answer

St1: No matter how many twins were born along with 33 singles total number will always be odd. SUFF
St2: We need to know the no. of singles to ascertain whether the total was odd. INSUFF

Ans : A

healthjunkie · Answer

I quickly set up the formula

S +2T= X . From the formula you can realize that the number of twins will always be even (there's 2 of them) so you can look at this as S + Even= Odd? Thus the question can be rephrased as is the number of single babies born odd? Thus statement 1 sufficient and statement 2 insufficient.

EMPOWERgmatRichC · Answer

Hi All,

This DS prompt serves as a nice example of how doing some 'up-front' work BEFORE you deal with the 2 Facts can help you to spot any inherent patterns in the question.

Here, we're told that we have a certain number of single babies and a certain number of twins born in a hospital. We're told that the TOTAL number of babies is X. We're asked if X is ODD?

Since twins come 'two-at-a-time', there will always be an EVEN number of twins. It's the number of SINGLE babies that will determine whether X is ODD or EVEN. Making THAT deduction up front makes dealing with the 2 Facts a remarkably simple task.

If you get in the habit of taking notes and putting in a little work up-front, you'll find that a number of DS questions on Test Day become considerably easier to answer.

GMAT assassins aren't born, they're made,
Rich

daviddaviddavid · Answer

yes youre right. I got it wrong and you cannot image how I feel about it

Luckisnoexcuse · Answer

I will go with A

(1) 33 is odd and twins are even so odd + even will always be odd ...sufficient

(2) twin is even but single birth/s can be even or odd. Hence insufficient

Sent from my iPhone using GMAT Club Forum

Elite097 · Answer

Bunuel   KarishmaB   MartyTargetTestPrep   ScottTargetTestPrep   avigutman  pls clarify the wording "one of a pair twins" . Does this not mean 1 out of the two twins were born at the hospital? As per that A is insufficient because we do not know the number of pairs. If number of pairs are odd then the number of that "one of the twins" born will also be odd. I am really not clear

EMPOWERgmatRichC · Answer

Hi Elite097, To answer your question, you have to actually read the ENTIRE first sentence. It states: "EACH baby born at a certain hospital last week was either a single birth or one of a pair twins." This tells us that EACH of the babies (whether from a single birth or as one fro a birth of twins) was born at a hospital. In other words, ALL of the babies mentioned were born at the hospital. GMAT assassins aren't born, they're made, Rich Contact Rich at: Rich.C@empowergmat.com

shwetakoshija · Answer

Given :
• Each baby was either a single birth or part of a pair of twins.
• Total number of babies = x.

To Find : Is x odd?

Statement 1 : There were 33 single births.
• These 33 babies contribute 33 (an odd number) to x. 
• Also, any number of twins born will always contribute an even number (since twins come in pairs).
• Hence, x = single births + 2(pairs of twins) = Odd + Even =  Odd .
• No matter how many pairs of twins were born, x will always be odd.

Statement 1 alone is sufficient.

Statement 2 : There were 3 pairs of twins born.
• These contribute 3 × 2 = 6 babies (an even number) to x.
• However, we know nothing about the number of single births. It could be Even or Odd.
• Hence, x = 6 + Even = Even OR x = 6 + Odd = Odd.

Statement 2 alone is insufficient.

Correct Answer: A

rak08 · Answer

A because basically

X = 2n+ single kid

if single kid = odd then x will always be odd because odd+even = odd (only)

Each baby born at a certain hospital last week was either a single bir

Prep Toolkit

Top 5 GMAT Debrief Videos

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

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Data Sufficiency (DS) Questions

Each baby born at a certain hospital last week was either a single bir

Prep Toolkit

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

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards