Henry Ernest Dudeney/Puzzles and Curious Problems/144 - Biblical Arithmetic/Solution

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Puzzles and Curious Problems by Henry Ernest Dudeney: $144$

Biblical Arithmetic
If you multiply the number of Jacob's sons by the number of times which the Israelites compassed Jericho on the seventh day,
and add to the product the number of measures of barley which Boaz gave Ruth,
divide this by the number of Haman's sons,
subtract the number of each kind of clean beasts that went into the Ark,
multiply by the number of men that went to seek Elijah after he was taken to Heaven,
subtract from this Joseph's age at the time he stood before Pharaoh,
add the number of stones in David's bag when he killed Goliath,
subtract the number of furlongs that Bethany was distant from Jerusalem,
divide by the number of anchors cast out when Paul was shipwrecked,
subtract the number of persons saved in the Ark,
and the answer will be the number of pupils in a certain Sunday school class.
How many people in the class?


Solution

There were $7$ in the Sunday school class.


Proof

Let us gird up our armour and proceed.

From Genesis $35 : 23$:

Jacob had $12$ sons while living in Aram-Naharaim.

From Joshua $6 : 15$:

On the $7$th day, the army got up at daybreak. They marched slowly around Jericho the same as they had done for the past $6$ days, except on this day they went around $7$ times.

From Ruth $3 : 15$:

[Boaz] also said, "Bring me the shawl you are wearing and hold it out." When she did so, he poured into it $6$ measures of barley and placed the bundle on her.

From Esther $9 : 10$:

... the $10$ sons of Haman son of Hammedatha, the enemy of the Jews.

From Genesis $7 : 2$:

Take with you $7$ pairs of every kind of clean animal, a male and its mate

(Technically this is $14$, but the answer given in the book reveals that $7$ is what is meant.)

From $\text {II}$ Kings $2 : 17$:

And they sent $50$ men, who searched for $3$ days but did not find him.

From Genesis $41 : 46$:

Joseph was $30$ years old when he entered the service of Pharaoh king of Egypt.

From $\text I$ Samuel $17 : 14$:

Then [David] took his staff in his hand, chose $5$ smooth stones from the stream, put them in the pouch of his shepherd's bag and, with his sling in his hand, approached the Philistine.

From John $11 : 18$:

Now Bethany was nigh unto Jerusalem, about $15$ furlongs off.

From Acts $27 : 29$:

Then fearing lest we should have fallen upon rocks, they cast $4$ anchors out of the stern, and wished for the day.

From Genesis $7 : 13$:

In the selfsame day entered Noah, and Shem, and Ham, and Japheth, the sons of Noah, and Noah's wife, and the $3$ wives of his sons with them, into the ark

That makes $8$, then.


It remains to perform the arithmetic.

Hence:

\(\ds \) \(\) \(\ds \paren {\paren {\paren {12 \times 7 + 6} \div 10 - 7} \times 50 - 30 + 5 - 15} \div 4 - 8\)
\(\ds \) \(=\) \(\ds \paren {\paren {90 \div 10 - 7} \times 50 - 30 + 5 - 15} \div 4 - 8\)
\(\ds \) \(=\) \(\ds \paren {2 \times 50 - 30 + 5 - 15} \div 4 - 8\)
\(\ds \) \(=\) \(\ds 60 \div 4 - 8\)
\(\ds \) \(=\) \(\ds 7\)

$\blacksquare$


Sources

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