If Company M ordered a total of 50 computers and printers an

The rule is that you need to have n "distinct" equations to solve to "n" variables. This is especially true for DS questions. Do not mark C or E in DS questions without actually loooking at the equations you get either from the question stem and the statements. This is the "pattern" you are talking about.

You get the same equations of \(C_m + P_m = 50\) from the question stem+2 statements combined.

Thus, be very careful in DS questions when you are given 'n' variables and 'n' equations. These equations must be distinct to give any unique value.

Hope this helps.
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It's straight E. Consider the following cases:

#1: M ordered 5 computers and 45 printers, N ordered 5 computers and 55 printers;
#2: M ordered 10 computers and 40 printers, N ordered 10 computers and 50 printers;

P.S. Please read carefully and follow: rules-for-posting-please-read-this-before-posting-133935.html
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I found this q weird.
For M, C(M) + P(M) = 50
For N, C(N)+ P(N) = 60

A does not say anything about printers for M and N. It can be 10 and 10, 20 and 20, 30 and 30 or any such combi
B same issue as A
On Combining, the info in both options is ambiguous. M and N computers are same where B says N has 10 more than M. How both of them can be true?

for me E should be the answer.......weird question, considering the source is from gmatprep....
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This is absolute killer.

This looks straight forward at first. From the question, two equations are introduced and four variables are introduced.

Then (1) and (2) each introduce what appears to be an additional equation so we have four equations and four variables.

At this point I selected answer C without solving assuming that our variable could be solved by rules of solvability with 4 equations. The problem is that the equation that (2) introduces is in fact identical to the information you already have. In essence it is not a new equation and thus you are still left with 4 variables and only 3 equations.

Does anyone have a more succinct way to explain this or identify this pattern in future problems?

Well said, and thank you for the response. The problem here was that an additional equation was introduced but it was not distinct.

Admins can you please edit this question take this part out "I get stuck in this one!Why is not C the right answer??? " sothat one cannot see the answer. Thanks.

Company M: a+b=50, Company N: x+y=60, b=?

(1) a=x, ok, y-b=10, not sufficient
(2) y=b+10 same information as above, not sufficient
(1)+(2) We have twice the same info, so still not sufficient.

Answer E

Bunuel

Hey!
I am also stuck with this question. The above statements that you mentioned didn't give us a unique answer on their own. But when i am combining them, i am using this approach and reaching to an answer.

Let (M computers) MC = x
therefore, (M Printers) MP = 50-x .......(eq1)
On other hand NC = y
and NP= 60-y

Now statement 1 says : x=y ie. Company M and N ordered same number of computer.
Thus NP becomes 60-x (because NP WAS "60-y" and now x=y)
so now, NP= 60-x .........(eq2)

statement 2 says: NP=10MP

Now combining 1 and 2 gives us:
ie (60-x) = 10(50-x)

Please help

(2) says: Company N ordered 10 more printers than Company M, not 10 times as many.
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Straight E
(1) M and N bought same number of computer = {Both 20 computers} or {30 computers} or {40 computers} ..etc etc. Cannot find no. of printers by this information INSUFFICIENT
(2) N bought 10 more printers than N= {M-30 N-40} or {M-44 N-54} or {M-1 N-11} No. of printers is again variable INSUFFICIENT

COMBINE
MC & NC=25 MP=25 NP=35 [MP+MC= 50 NP+NC=60]
or
MC & NC=10 MP=40 NP=50 [MP+MC= 50 NP+NC=60]
or
MC & NC=1 MP=49 NP=59 [MP+MC= 50 NP+NC=60]
or
MC & NC=0 MP=50 NP=60 [MP+MC= 50 NP+NC=60]

Even afer combining the two statements number of printers that company M bought can be anything from 1 to 50

HENCE 0

DO NOT BE AFRAID TO CHOOSE E WHEN CALCULATIONS OBVIOUSLY POINTS THAT THE OPTION IS INDEED E


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From stimulus
mp+mc=50
np+nc=60
(1) Company M and Company N ordered the same number of computers
2*c +mp+np=110 ------------------> because (50+60=110)
INSUFFICIENT
(2) Company N ordered 10 more printers than Company M
mc+nc+2p=100--------------------------->because (110-10=100)
INSUFFICIENT

ADDING BOTH STATEMENTS
2C+2P=210
C+P=105

CANNOT FIGURE INDIVIDUAL VALUE OF COMPUTER AND PRINTERS

INSUFFICIENT

E IS ANSWER
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Given :

Company M :
C1 + P1 = 50 >> C1=50 - P1 --------(1)
Company N :
C2 + P2 = 60 >> C2=60 - P2 --------(2)

To find : C1 = ?

Basically statement(1) and statement(2) are representing the same information
Hence, definitely (C) cannot be the answer.

statement(1) : Company M and Company N ordered the same number of computers
C1=C2
from(1) & (2)
50 - P1 = 60 - P2 >> P2 - P1 = 10
not sufficient to calculate C1.

statement(2) : Company N ordered 10 more printers than Company M
Algebraically , P2 - P1 = 10 (same as statement (2))

Hence, none of the statements are sufficient to answer the question

Ans : E

My takeaway from the free info was that these two companies each ordered some mix of computers and printers, such that N ordered 10 more (overall) than M did.
Then when I read statement 1, I made the inference that N must've ordered 10 more printers than M did.
But... That's exactly what statement 2 says!!!

So then I wondered whether statement 2 implies statement 1, just as statement 1 implied statement 2... And, it does!

That eliminates ABC automatically (without even looking at what the question is asking). I explain this in section 2 of my book (these are inferentially equivalent statements).

Since neither statement is sufficient on its own, that leaves us with E.
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