Which of the following number is rational
A. 2(square root of 5)
B. square root of 25
C. 2pie
D. 25pie
Please help

Question

Which of the following number is rational
A. 2(square root of 5)
B. square root of 25
C. 2pie
D. 25pie
Please help

anonymous · Answer

A rational number means that the number ends at some point. Since pi never ends, it can't be C or D. If you enter 2sqrt(5) into a calculator, you'll also get a never ending decimal. So the answer must be B, by process of elimination. But also because the square root of 25 is 5, and 5 is rational.

whpalmer4 · Answer

no, a rational number means that it can be represented by a fraction of two integers...1/7 is a rational number, but the decimal expansion is 0.142857142857142857 repeating without end.

anonymous · Answer

so which one is it? I cant figure it out

whpalmer4 · Answer

$\pi$ is known to be irrational, so any multiple of $\pi$ is also irrational.

the square root of 5 is irrational.  the square root of 25 = 5 and so is rational.  even if we weren't sure about the square root of 5, we know that the square root of 25 is rational.  therefore, knowing there is only one correct answer, we choose square root of 25 and assume square root of 5 is irrational.

anonymous · Answer

so its b?

whpalmer4 · Answer

the only choice there which is a rational number is the square root of 25.  you'll have to figure out which letter that is, I'm only concerned with the math part :-)