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Updated on: 28 Sep 2020, 01:37
Originally posted by MathRevolution on 28 Sep 2020, 01:26.
Last edited by MathRevolution on 28 Sep 2020, 01:37, edited 1 time in total.
Last edited by MathRevolution on 28 Sep 2020, 01:37, edited 1 time in total.
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Forget the conventional way to solve DS questions.
We will solve this DS question using the variable approach.
DS question with 2 variables : Let the original condition in a DS question contain 2 variables . In other words, there are two fewer equations than variables. Now, we know that each condition (1) and (2) would usually give us an equation, however, since we need 2 equations to match the numbers of variables and equations in the original condition, the unequal number of equations and variables should logically give us an answer C.
To master the Variable Approach, visit https://www.mathrevolution.com and check our lessons and proven techniques to score high in DS questions.
Let’s apply the 3 steps suggested previously. [Watch lessons on our website to master these 3 steps]
Step 1 of the Variable Approach: Modifying and rechecking the original condition and the question.
We have to find value of the two digit number 'x'.
=> Let us assign variable to the digits: Ten's place(a) and Unit's place (b).
=> x = 10a + b
Second and the third step of Variable Approach: From the original condition, we have 2 variables (a and b).To match the number of variables with the number of equations, we need 2 equations. Since conditions (1) and (2) will provide 1 equation each, C would most likely be the answer.
Let’s take a look at both conditions together .
Condition(1) tells us that the sum of the two digits is 4 .
=> a + b = 4 ----------(1)
Condition(2) tells us that the difference between the two digits is 2.
=> a - b = 2 ----------(2)
=> Adding both equations gets us 2a = 6 or a = 3 and b = 1.
So, number formed will be 31. But, if we interchange 'a' and 'b' then number formed will be 13 which satisfies both the conditions too.
Since the answer is not unique, both conditions together are not sufficient by CMT 2.
So, E is the correct answer.
Answer: E
We will solve this DS question using the variable approach.
DS question with 2 variables : Let the original condition in a DS question contain 2 variables . In other words, there are two fewer equations than variables. Now, we know that each condition (1) and (2) would usually give us an equation, however, since we need 2 equations to match the numbers of variables and equations in the original condition, the unequal number of equations and variables should logically give us an answer C.
To master the Variable Approach, visit https://www.mathrevolution.com and check our lessons and proven techniques to score high in DS questions.
Let’s apply the 3 steps suggested previously. [Watch lessons on our website to master these 3 steps]
Step 1 of the Variable Approach: Modifying and rechecking the original condition and the question.
We have to find value of the two digit number 'x'.
=> Let us assign variable to the digits: Ten's place(a) and Unit's place (b).
=> x = 10a + b
Second and the third step of Variable Approach: From the original condition, we have 2 variables (a and b).To match the number of variables with the number of equations, we need 2 equations. Since conditions (1) and (2) will provide 1 equation each, C would most likely be the answer.
Let’s take a look at both conditions together .
Condition(1) tells us that the sum of the two digits is 4 .
=> a + b = 4 ----------(1)
Condition(2) tells us that the difference between the two digits is 2.
=> a - b = 2 ----------(2)
=> Adding both equations gets us 2a = 6 or a = 3 and b = 1.
So, number formed will be 31. But, if we interchange 'a' and 'b' then number formed will be 13 which satisfies both the conditions too.
Since the answer is not unique, both conditions together are not sufficient by CMT 2.
So, E is the correct answer.
Answer: E
28 Sep 2020, 01:52
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Asked: What is the value of the two-digit number x?
Let x be ab where a is tenth digit and b is unit digit of x.
(1) The sum of the two digits is 4.
a + b = 4
x = {13,31,22,40}
NOT SUFFICIENT
(2) The difference between the two digits is 2.
x = {20,13,31,24,42,35,53,46,64,57,75,68,86,79,97}
NOT SUFFICIENT
(1) + (2)
(1) The sum of the two digits is 4.
(2) The difference between the two digits is 2.
x = {13,31}
NOT SUFFICIENT
IMO E
Let x be ab where a is tenth digit and b is unit digit of x.
(1) The sum of the two digits is 4.
a + b = 4
x = {13,31,22,40}
NOT SUFFICIENT
(2) The difference between the two digits is 2.
x = {20,13,31,24,42,35,53,46,64,57,75,68,86,79,97}
NOT SUFFICIENT
(1) + (2)
(1) The sum of the two digits is 4.
(2) The difference between the two digits is 2.
x = {13,31}
NOT SUFFICIENT
IMO E
