Is the range of a combined set (S,T) bigger than the sum of

Question

Is the range of a combined set (S,T) bigger than the sum of ranges of sets S and T ?

(1) The largest element of T is bigger than the largest element of S. 
(2) The smallest element of T is bigger than the largest element of S.

M13-26

Bunuel · Accepted Answer

The range of a set is the difference between the largest and smallest elements of a set.

range_t=t_{max}-t_{min} ;
 range_s=s_{max}-s_{min} ;

Question:  range_{t&s}>t_{max}-t_{min}+s_{max}-s_{min} ?

(1) The largest element of T is bigger than the largest element of S -->  t_{max}>s_{max} , so the largest element of combined set is  t_{max}  but we still don't know which is the smallest element of combined set:

If it's  t_{min}  then the question becomes is  t_{max}-t_{min}>t_{max}-t_{min}+s_{max}-s_{min}  --> is  0>s_{max}-s_{min}  and the answer would be NO;
If it's  s_{min}  then the question becomes is  t_{max}-s_{min}>t_{max}-t_{min}+s_{max}-s_{min}  --> is  t_{min}>s_{max}  and the answer would be sometimes NO and sometimes YES.

Not sufficient.

(2) The smallest element of T is bigger than the largest element of S -->  t_{min}>s_{max} , so the largest of combined set is  t_{max}  and the smallest element of combined set is  s_{min} .

So the question becomes is  t_{max}-s_{min}>t_{max}-t_{min}+s_{max}-s_{min}  --> is  t_{min}>s_{max}  and the answer is YES.

Sufficient.

Answer: B.

prashantbacchewar · Answer

Thanks Bunuel great explaination

MathRevolution · Answer

Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

Is the range of a combined set (S,T) bigger than the sum of ranges of sets S and T ?

(1) The largest element of T is bigger than the largest element of S. 
(2) The smallest element of T is bigger than the largest element of S.

Modify the original condition and the question. In order to satisfy the question ‘Is the range of a combined set (S,T) bigger than the sum of ranges of sets S and T?,’ the 2 sets of S and T shouldn’t be overlapped. For instance, if S={1,2} T={100,101}, it is yes. Thus, if you look at 2), there is no overlap, which is sufficient.
Therefore, the answer is B.

 Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.

manojach87 · Answer

Let S= {x,...,y} where x is the smallest element and y is the largest element in set S 
Let T= {z,...,a} where z is the smallest element and a is the largest element in set T 
Let Range of Set S and T combined =  R_{st} 
Let Range of Set S =  R_s 
Let Range of Set T =  R_t

Question :  R_{st} >  R_s  +  R_t

1. a>y

\begin{array}{c|c|c|c|c|c|c|c|c}
 x & y & z & a &  R_s  &  R_t  &  R_s + R_t  &  R_{st}  &  R_{st}  >  R_s + R_t  \ 
 \hline
 1 & 2 & 1 & 3 & 1 & 2 & 3 & 2 &2>3? No \
 1 & 1 & 2 & 2 & 0 & 0 & 0 & 1 &1>0? Yes \
 \hline
 \end{array}

Yes and No. Hence Not Sufficient
2. z>y
\begin{array}{c|c|c|c|c|c|c|c|c}
 x & y & z & a &  R_s  &  R_t  &  R_s + R_t  &  R_{st}  &  R_{st}  >  R_s + R_t  \ 
 \hline
 1 & 2 & 3 & 3 & 1 & 0 & 1 & 2 & 2>1 ? Yes \
 1 & 1 & 2 & 2 & 0 & 0 & 0 & 1 & 1>0 ? Yes \
 1 & 2 & 3 & 4 & 1 & 1 & 2 & 3 & 3>2 ? Yes \
 \hline
 \end{array}

Always Yes. Hence Sufficient

Hence answer is B.

tyildirim92 · Answer

Refer to the picture

bumpbot · Answer

Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.

Is the range of a combined set (S,T) bigger than the sum of

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

Is the range of a combined set (S,T) bigger than the sum of

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