Henry Ernest Dudeney/Modern Puzzles/27 - The First-Born's Legacy/Solution

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Modern Puzzles by Henry Ernest Dudeney: $27$

The First-Born's Legacy
Mrs. Goodheart gave birth to twins.
The clock showed clearly that Tommy was born about an hour later than Freddy.
Mr. Goodheart, who died a few months earlier, had made a will leaving $\pounds 8400$,
and had taken the precaution to provide for the possibility of there being twins.
In such a case the money was to be divided in the following proportions:
two-thirds to the widow,
one-fifth to the first-born,
one-tenth to the other twin,
and one-twelfth to his brother.
Now, what is the exact amount that should be settled on Freddy?


Solution

Freddy gets $\pounds 800$.


Dudeney performs the arithmetic that determines the exact sums to be bestowed:

Mrs. Goodheart gets $\dfrac {43} {63} \times \pounds 8400 = \pounds 5333 \tfrac 1 3 = \pounds 5333 \ 6 \shillings 8 \oldpence$
the first-born gets $\dfrac {12} {63} \times \pounds 8400 = \pounds 1600$
the second-born gets $\dfrac 6 {63} \times \pounds 8400 = \pounds 800$
his brother gets $\dfrac 5 {63} \times \pounds 8400 = \pounds 666 \tfrac 2 3 = \pounds 666 \ 13 \shillings 4 \oldpence$


He then goes on to say:

But the sting is in the tail, and the question is indeterminate.

What is "indeterminate" is what is meant by "his brother".

Dudeney goes on to explain that the twins were born either side of the time at which the clock went back at the end of British Summer Time.

Hence Tommy was actually the first-born and Freddy the younger of the two.


A pencil-written marginal note in the second-hand copy possessed by prime.mover says:

Silly

with which prime.mover concurs.


Proof

We first note that $\dfrac 2 3 + \dfrac 1 5 + \dfrac 1 {10} + \dfrac 1 {12} = \dfrac {40 + 12 + 6 + 5} {60} = \dfrac {63} {60}$.

As this is greater than $1$, we must interpret the question as that the legacies are in the appropriate proportions.

Hence:

Mrs. Goodheart gets $\dfrac {43} {63} \times \pounds 8400 = \pounds 5333 \tfrac 1 3 = \pounds 5333 \ 6 \shillings 8 \oldpence$
the first-born gets $\dfrac {12} {63} \times \pounds 8400 = \pounds 1600$
the second-born gets $\dfrac 6 {63} \times \pounds 8400 = \pounds 800$
his brother gets $\dfrac 5 {63} \times \pounds 8400 = \pounds 666 \tfrac 2 3 = \pounds 666 \ 13 \shillings 4 \oldpence$


According to the question, it appears that in fact Freddy is the first-born.

However, Dudeney pulls a new fact out of his hat:

Tommy was actually born when the clock showed just before $2$ a.m. on $21$st September $1924$
At $2$ a.m. the clocks went back $1$ hour, as British Summer Time ended at that point
Freddy was born soon after $1$ a.m. by the clock, but before $2$ a.m.

Hence Tommy is actually the first-born, and not Freddy.

So Freddy gets $\pounds 800$.

$\blacksquare$


Sources

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