Civil Services Prep

Prelims 2022 · CSAT / Quantitative Aptitude · Question 67

Consider the following statements in respect of two natural numbers p and q such that p is a prime number and q is a composite number:<br/>1. p x q can be an odd number.<br/>2. q / p can be a prime number.<br/>3. p + q can be a prime number.<br/><br/>Which of the above statements are correct?

  1. 1 and 2 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3

Answer

1, 2 and 3

1. p × q can be odd if both are odd. A prime can be odd (e.g. p = 3) and a composite can also be odd (e.g. q = 9), so 3 × 9 = 27 is odd. Verdict: Correct.

2. q / p can be a prime number if q is a composite multiple of p. Example: p = 2, q = 6 gives q/p = 3, which is prime. Verdict: Correct.

3. p + q can be a prime number. Example: p = 2 and q = 9 gives 2 + 9 = 11, which is prime. Verdict: Correct.

Hence, all three statements are correct.

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