Henry Ernest Dudeney/Puzzles and Curious Problems/105 - Equal Fractions/Solution
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Puzzles and Curious Problems by Henry Ernest Dudeney: $105$
- Equal Fractions
- Can you construct three ordinary vulgar fractions
- (say, $\tfrac 1 2$, $\tfrac 1 3$, or $\tfrac 1 4$, or anything up to $\tfrac 1 9$ inclusive)
- all of the same value, using in every group all the nine digits once, and once only?
- The fractions may be formed in one of the following ways:
- $\dfrac a b = \dfrac c d = \dfrac {e f} {g h j}$, or $\dfrac a b = \dfrac c {d e} = \dfrac {f g} {h j}$.
- We have only found five cases, but the fifth contains a simple little trick that may escape the reader.
Solution
The examples given by Dudeney are:
- $\dfrac 2 4 = \dfrac 3 6 = \dfrac {79} {158}$
- $\dfrac 3 6 = \dfrac 7 {14} = \dfrac {29} {58}$
- $\dfrac 3 6 = \dfrac 9 {18} = \dfrac {27} {54}$
- $\dfrac 2 6 = \dfrac 3 9 = \dfrac {58} {174}$
The fifth case which he offers up is:
- $\dfrac {\cdotp 2} 1 = \dfrac {\cdotp 6} 3 = \dfrac {97} {485}$
where it is noted that the first two fractions are not actually proper fractions.
It is worth calling into question Dudeney's definition of a vulgar fraction, as he is unclear.
Sources
- 1932: Henry Ernest Dudeney: Puzzles and Curious Problems ... (previous) ... (next): Solutions: $105$. -- Equal Fractions
- 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Answers: $133$. Equal Fractions