Which number produces an irrational number when multiplied by 1/3?

Accepted Solution

A number multiplied by 13 only produces an irrational number if it is itself an irrational number.Explanation:Suppose there were some rational number which when multiplied by 13 generated an irrational number.If the number is rational then, by definition, it can be expressed as ab for some pair of integers a and b.ab×13=a×1b×3=a3bSince a is an integer and 
since if b is an integer then 3b is also an integer,
by definition a3b is a rational number, contrary to our supposition that some rational number ab when multiplied by 13 could generate an irrational number.