MathDB

A

takes

m

times as long to do a piece of work as

B

and

C

together;

B

takes

n

times as long as

C

and

A

together; and

C

takes

x

times as long as

A

and

B

together. Then

x

, in terms of

m

and

n

, is: (A)\ \frac {2mn}{m \plus{} n} \qquad (B)\ \frac {1}{2(m \plus{} n)} \qquad (C)\ \frac {1}{m \plus{} n \minus{} mn} \qquad (D)\ \frac {1 \minus{} mn}{m \plus{} n \plus{} 2mn} \qquad (E)\ \frac {m \plus{} n \plus{} 2}{mn \minus{} 1}

Problem Statement