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20 Nov 2015, 10:14
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M and N are positive numbers. Is N > 0.06?
This is a yes or no type DS question.
Taking choice 1
(1) When M + N is rounded to tenths digit the value is M
M + N = M
a)Lets take M = 4.2, N= 0.04 M+ N rounded off to tenth digit equals 4.2 +0.04 = 4.24 which is 4.2 equal to M and satisfies M+N =M.
b)Lets take M=4.2, N=0.05 M+ N rounded off to tenth digit equals 4.2 +0.05 = 4.25 which is 4.3 and not equal to M and doesn't satisfy M+N =M.
Therefore N<0.05 and hence choice A is sufficient to answer the question.
(2) Taking choice 2 N > 0.04
N can be any value greater than 0.04, that is 0.05 or 0.07, which can be either Greater than or lesser than 0.06. So choice B is not sufficient.
So answer is choice A.
This is a yes or no type DS question.
Taking choice 1
(1) When M + N is rounded to tenths digit the value is M
M + N = M
a)Lets take M = 4.2, N= 0.04 M+ N rounded off to tenth digit equals 4.2 +0.04 = 4.24 which is 4.2 equal to M and satisfies M+N =M.
b)Lets take M=4.2, N=0.05 M+ N rounded off to tenth digit equals 4.2 +0.05 = 4.25 which is 4.3 and not equal to M and doesn't satisfy M+N =M.
Therefore N<0.05 and hence choice A is sufficient to answer the question.
(2) Taking choice 2 N > 0.04
N can be any value greater than 0.04, that is 0.05 or 0.07, which can be either Greater than or lesser than 0.06. So choice B is not sufficient.
So answer is choice A.
21 Nov 2015, 09:58
Kudos
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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.
M and N are positive numbers. Is N > 0.06?
(1) When M + N is rounded to tenths digit the value is M
(2) N > 0.04
There are 2 variables (m,n) and 2 equations are given from the 2 conditions.
Looking at the conditions together, m and n has to be numbers like n=0.041, m=1.201, so that m+n=1.242
and n=0.041<0.06, so this answers the question 'no' and is sufficient, making the answer seem like (C).
However, this is a integer question, one of the key question. If we apply the common mistakes type 4(A),
Condition 1) If n>0.06, the tenth digit of m cannot be rounded up so this is 'no' and sufficient.
For condition 2, the answer is 'yes' for 0.07 but 'no' for n=0.05. This is insufficient as the range of the condition is not included in that of the question.
Therefore, the answer becomes (A).
For cases where we need 2 more equation, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.
M and N are positive numbers. Is N > 0.06?
(1) When M + N is rounded to tenths digit the value is M
(2) N > 0.04
There are 2 variables (m,n) and 2 equations are given from the 2 conditions.
Looking at the conditions together, m and n has to be numbers like n=0.041, m=1.201, so that m+n=1.242
and n=0.041<0.06, so this answers the question 'no' and is sufficient, making the answer seem like (C).
However, this is a integer question, one of the key question. If we apply the common mistakes type 4(A),
Condition 1) If n>0.06, the tenth digit of m cannot be rounded up so this is 'no' and sufficient.
For condition 2, the answer is 'yes' for 0.07 but 'no' for n=0.05. This is insufficient as the range of the condition is not included in that of the question.
Therefore, the answer becomes (A).
For cases where we need 2 more equation, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.
28 Nov 2015, 08:57
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Bunuel
GMAT Club reserves the rights to modify the terms of this offer at any time. JAMBOBREE OFFICIAL SOLUTION:
The rounding concept is that when have to round up the number to any particular position we check just the next right hand digit of the number , if the next right hand number is less than 5 then we keep the digit in the position which we need to round of same but if the next right hand number is greater than or equal to 5 then we increase by 1 the digit in the position which we need to round of.
Statement 1
Let us consider M = ABC. DEF and N = rst.uvs
Where A,B,C,D,E,F,r,s,t,u,v,and s are the digits of numbers M and N
Now it is given that When M + N is rounded to tenths digit the value is M
The above will only be true if r=s=t=u =0 .
also E+ v < 5 --> v < 5
hence N < 0.5 --> N < 0.6
hence we have a definite No as the definite answer
statement 1 is sufficient.
Statement 2
Now N > 0.04 does not answer the question as N can be either 0.5 or 0.8
Answer: A.
GMAT Club reserves the rights to modify the terms of this offer at any time. 
