Henry Ernest Dudeney/Puzzles and Curious Problems/114 - Elementary Arithmetic/Solution

by : $114$

 * Elementary Arithmetic

Solution

 * $2 \tfrac 2 3$

Proof
According to, this is:
 * merely a sum in simple proportion:

If $5$ be $4$, then:
 * $3 \tfrac 1 3$ is $3 \tfrac 1 3 \times \dfrac 4 5 = \dfrac {10 \times 4} {3 \times 5} = 2 \tfrac 2 3$