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If a and b are positive integers, is (a + b) prime?
Statement 1: 13a = 43b
Statement 2: 8a = 15b
  • a)
    Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient
  • b)
    Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient
  • c)
    Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
  • d)
    EACH statement ALONE is sufficient
  • e)
    Statements (1) and (2) TOGETHER are NOT sufficient
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
If a and b are positive integers, is (a + b) prime?Statement 1: 13a = ...
Step 1: Evaluate Statement 1 ALONE
Statement 1: 13a = 43b
a/b = 43/13
a : b :: 43 : 13
So, a = 43x and b = 13x
a + b = 43x + 13x = 56x
56 is not prime. Therefore, 56x cannot be prime.
We are able to answer the question with a DEFNITE NO.
Hence, statement 1 alone is sufficient.
Eliminate answer option B, C, and E.
Step 2: Evaluate Statement 2 ALONE
Statement 2: 8a = 15b
a/b = 15/8
a : b :: 15 : 8
So, a = 15x and b = 8x
a + b = 15x + 8x = 23x
23 is prime.
If x is 1, a + b will be prime. For other values of x, a + b will not be prime.
We are not able to answer the question with a DEFNITE Yes or No.
Hence, statement 2 alone is not sufficient.
Eliminate answer option D.
Statement 1 alone is sufficient. Statement 2 is NOT sufficient.
Choice A is the correct answer.
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Most Upvoted Answer
If a and b are positive integers, is (a + b) prime?Statement 1: 13a = ...
To determine if (a + b) is prime, we need to find the values of a and b. Let's analyze each statement separately:

Statement 1: 13a = 43b
- This equation relates the values of a and b. We can rewrite it as a = (43b)/13.
- Since a and b are positive integers, the value of (43b)/13 must also be an integer.
- However, we can't determine if (a + b) is prime from this information alone. We don't have any specific values for a or b.

Statement 2: 8a = 15b
- This equation also relates the values of a and b. We can rewrite it as a = (15b)/8.
- Since a and b are positive integers, the value of (15b)/8 must also be an integer.
- Again, we can't determine if (a + b) is prime from this information alone. We don't have any specific values for a or b.

Now, let's consider both statements together:

From statement 1, we have a = (43b)/13, and from statement 2, we have a = (15b)/8.
- Since both expressions are equal to a, they must be equal to each other: (43b)/13 = (15b)/8.
- We can cross multiply to solve for b: 43b * 8 = 13 * 15b.
- Simplifying, we get 344b = 195b.
- Dividing both sides by b, we get 344 = 195.
- This is a contradiction, as 344 is not equal to 195.
- Therefore, the two statements together lead to an inconsistency, and we still can't determine if (a + b) is prime.

Since neither statement alone is sufficient to determine if (a + b) is prime and the two statements together are also not sufficient, the correct answer is option A: Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
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