If y is an integer, is y3 divisible by 9?1) y is divisible by 42) y is...
(1) Take multiples of 4 and 9 and the answer is yes, but say for numbers that are only multiples of 4, the answer is No
(2) is sufficient because y is divisible by 6 means that y has 3 as factor, hence y^3 will have 3^3 as factor
=> y^3 is divisible by 9.
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If y is an integer, is y3 divisible by 9?1) y is divisible by 42) y is...
Solution:
We need to determine whether y^3 is divisible by 9 or not.
We know that 9 = 3^2. So, for a number to be divisible by 9, it must be divisible by 3^2.
Let's evaluate the given statements.
Statement 1: y is divisible by 4
4 = 2^2. So, if y is divisible by 4, it must also be divisible by 2^2.
Let's consider some values of y to see whether y^3 is divisible by 9 or not.
If y = 4, then y^3 = 64, which is not divisible by 9.
If y = 8, then y^3 = 512, which is not divisible by 9.
If y = 12, then y^3 = 1728, which is divisible by 9.
From the above values, we can see that statement 1 alone is not sufficient to answer the question.
Statement 2: y is divisible by 6
6 = 2 x 3. So, if y is divisible by 6, it must also be divisible by both 2 and 3.
Let's consider some values of y to see whether y^3 is divisible by 9 or not.
If y = 6, then y^3 = 216, which is divisible by 9.
If y = 12, then y^3 = 1728, which is divisible by 9.
If y = 18, then y^3 = 5832, which is divisible by 9.
From the above values, we can see that statement 2 alone is sufficient to answer the question.
Combining both statements, we know that y is divisible by 4 and 6. This means y must be divisible by 2^2 and 2 x 3. So, y must be divisible by 3 and hence, y^3 must be divisible by 3^2 = 9.
Therefore, both statements together are required to answer the question.
Hence, the correct answer is option (B).
If y is an integer, is y3 divisible by 9?1) y is divisible by 42) y is...
Exactly one statement is enough i.e., y is divisible by 6
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