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Question

Is the two digit number odd?

Statement 1 (S1) : Sum of the digits is even

Statement 2 (S2) : The number, when multiplied by 2, fetches an even number.

The correct answer is

Both S1 & S2 combined are not sufficient to answer the question.

To determine if a two-digit number is odd, we need to analyze the information provided in Statement 1 (S1) and Statement 2 (S2).

Two-Digit Number Definition

Let the two-digit number be represented as \(N\). A two-digit number ranges from 10 to 99. We can express \(N\) as \(10a + b\), where \(a\) is the tens digit (\(a \in \{1, 2, ..., 9\}\)) and \(b\) is the units digit (\(b \in \{0, 1, ..., 9\}\)).

A number is considered odd if its units digit (\(b\)) is one of 1, 3, 5, 7, or 9.

A number is considered even if its units digit (\(b\)) is one of 0, 2, 4, 6, or 8.

Analyzing Statement 1 (S1): Sum of the Digits is Even

Statement 1 provides the condition that the sum of the digits, \(a + b\), is an even number.

For the sum of two integers to be an even number, there are exactly two possible scenarios for the parity (odd or even) of the individual digits:

  • Case 1: Both digits \(a\) and \(b\) are even.
    • If \(a\) is an even digit (e.g., 2, 4, 6, 8) and \(b\) is an even digit (e.g., 0, 2, 4, 6, 8), then their sum \(a+b\) will be an even number.
    • In this situation, the two-digit number \(N = 10a + b\). Since \(10a\) will always be an even number (as 10 is even) and \(b\) is specified as even, their sum \(N\) will be an even number.
    • Example: Consider the two-digit number \(N = 20\). Here, \(a=2\) (even) and \(b=0\) (even). The sum of digits is \(2+0=2\), which is even. The number 20 is an even number.
    • Example: Consider the two-digit number \(N = 42\). Here, \(a=4\) (even) and \(b=2\) (even). The sum of digits is \(4+2=6\), which is even. The number 42 is an even number.
  • Case 2: Both digits \(a\) and \(b\) are odd.
    • If \(a\) is an odd digit (e.g., 1, 3, 5, 7, 9) and \(b\) is an odd digit (e.g., 1, 3, 5, 7, 9), then their sum \(a+b\) will also be an even number.
    • In this situation, the two-digit number \(N = 10a + b\). Since \(10a\) will always be an even number and \(b\) is specified as odd, their sum \(N\) will be an odd number.
    • Example: Consider the two-digit number \(N = 11\). Here, \(a=1\) (odd) and \(b=1\) (odd). The sum of digits is \(1+1=2\), which is even. The number 11 is an odd number.
    • Example: Consider the two-digit number \(N = 35\). Here, \(a=3\) (odd) and \(b=5\) (odd). The sum of digits is \(3+5=8\), which is even. The number 35 is an odd number.

Since Statement 1 allows for the two-digit number \(N\) to be both odd (e.g., 11) and even (e.g., 20) while satisfying the condition, Statement 1 alone is not sufficient to definitively answer whether the two-digit number is odd.

Analyzing Statement 2 (S2): The Number, When Multiplied by 2, Fetches an Even Number

Statement 2 states that \(2 \times N\) is an even number.

  • The property of multiplication dictates that if any integer \(N\) is multiplied by 2, the result will always be an even number, regardless of whether \(N\) itself is odd or even.
  • Example: If \(N = 7\) (an odd number), then \(2 \times 7 = 14\), which is an even number.
  • Example: If \(N = 8\) (an even number), then \(2 \times 8 = 16\), which is an even number.

This statement provides no unique information that helps us determine the parity (odd or even) of \(N\) itself. It is a universal truth for all integers.

Therefore, Statement 2 alone is not sufficient to answer whether the two-digit number is odd.

Combining Both Statements (S1 & S2)

When we combine Statement 1 and Statement 2, we consider the implications of both conditions simultaneously to see if a definitive answer can be reached.

As previously established, Statement 2 does not offer any useful additional information to determine if the two-digit number is odd, because multiplying any integer by 2 always yields an even number.

Consequently, combining the statements essentially means we are only relying on the information provided by Statement 1.

From our analysis of Statement 1, we observed that:

  • It allows for cases where the two-digit number \(N\) is even (e.g., \(N=20\), where \(a=2, b=0\), sum of digits \(2+0=2\) is even, and 20 is even).
  • It also allows for cases where the two-digit number \(N\) is odd (e.g., \(N=11\), where \(a=1, b=1\), sum of digits \(1+1=2\) is even, and 11 is odd).

Since we can still find examples where the number is odd and examples where the number is even, even after considering both statements, we cannot definitively answer the question "Is the two-digit number odd?" with a simple "Yes" or "No".

Therefore, both Statement 1 and Statement 2 combined are not sufficient to answer the question.

Summary of Statement Analysis for Two-Digit Number Parity
Statement Condition Example (Number N) Is N odd? Sufficiency
S1: Sum of digits (\(a+b\)) is even \(a\) even, \(b\) even \(N=20\) (\(2+0=2\)) No (20 is even) Not Sufficient (allows both odd and even numbers)
\(a\) odd, \(b\) odd \(N=11\) (\(1+1=2\)) Yes (11 is odd)
S2: The number, when multiplied by 2, fetches an even number (\(2N\) is even) Always true for any integer N \(N=10 \Rightarrow 20\) (even)
\(N=11 \Rightarrow 22\) (even)
Cannot determine N's parity Not Sufficient (provides no information about N itself)
S1 & S2 Combined Effectively same as S1 (S2 adds no value) Can be \(11\) (odd) or \(20\) (even) Cannot determine definitively Not Sufficient

Final Answer Conclusion

Based on the detailed analysis, neither Statement 1 alone, nor Statement 2 alone, nor both statements combined provide sufficient information to determine if the two-digit number in question is odd. We cannot give a definitive "Yes" or "No" answer.

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Important Questions from Data Sufficiency

  1. In this question, a question is followed by two statements numbered (I) and (II). You have to decide whether the data provided in the statements are sufficient to answer the question. Read both the statements and decide the appropriate answer.
    Q. Harsh, Ketan, Mayank, Rohit, and Sidharth, each have different height. Who is the shortest?
    (I) Mayank is taller than Harsh but shorter than Ketan.
    (II) Rohit is taller than Harsh but shorter than Mayank.
  2. In this question, a question is followed by two statements numbered (I) and (II). You have to decide whether the data provided in the statements are sufficient to answer the question. Read both the statements and decide the appropriate answer.
    Q. Kunal, Mohit, Rohan, Sandeep, and Tarun - each have different age. Who is the oldest?
    (I) Mohit is older than Kunal but younger than Sandeep.
    (II) Tarun is younger than Sandeep but older than Mohit.
  3. In this question, a question is followed by two statements numbered (I) and (II). You have to decide whether the data provided in the statements are sufficient to answer the question. Read both the statements and decide the appropriate answer.

    Question:
    Among 5 trees, L, M, N, T and V each having a different height, which tree is the shortest?

    Statements:
    (I) N is shorter than only three trees.
    (II) N is taller than M but shorter than T.
  4. Below is given a pair of questions, which are required to be answered, and a triad of statements. Which group of statements is sufficient to answer both the questions? 

    Question 1: Who is sitting opposite to Q? 

    Question 2: Who is sitting to the right of Q? 

    Statement 1 : P and U are sitting on left and right sides of T, respectively 

    Statement 2: P, Q, R, S, T and U are sitting around a round table with six chairs 

    Statement 3: Q is NOT sitting on the immediate left side of R

  5. Area of a rectangle with length x and breadth y is P and area of a parallelogram (which is strictly not a rectangle) with adjacent sides of length x and y is Q.
    Question : Is \(P > Q\)?
    Statement-I: \(x : y = 2 : 1\)
    Statement-II: The angle between the two adjacent sides of the parallelogram is \(60^\circ\).
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