Largest Product

Using all the digits from 1 to 7, what two numbers have the largest product? For example, 1234 x 567 = 699678 but you can do much better than that.

742 x 6531 = 4,846,002.

A similar problem can be found in L.A. Graham’s Ingenious Mathematical Problems and Methods with a range of 1 to 9, but the principle remains the same – the numbers with the smallest difference produce the largest product. You start out with the highest two digits, 7 and 6, then attach 5 and 4, putting the smaller of the two digits with the larger number, giving you 74 and 65. The next two highest digits are 3 and 2, giving you 742 and 653. Finally, you add the 1 to the lower number. Page 80 has the details of that solution.

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How Many Months Have 28 Days?

Some months have 30 days and some have 31 days. How many months have 28 days?

All of them. Every month has 28 days. Some just continue on after reaching 28.

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ROFORKAD

What does this rebus represent?

ROFORKAD

A fork in the road.

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The Train and the Tunnel

A train is a half mile long and is about to enter a 10 mile tunnel. If the train is traveling at 35mph, how long will it take for the entire train to make it through the tunnel, from the front of the train entering to the end of the train leaving the tunnel?

18 minutes.

Length of the train: 0.5 miles
Length of the tunnel: 10 miles
Total distance: 0.5 + 10 = 10.5 miles

Time = 10.5 miles / 35 mph = 0.3 hours = 18 minutes

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Cowboy Corral

Two cowboys live next door to each other and both have a corral for their cows in the back. One day they meet at the back of their homes, standing next to a wall dividing their corrals. The first cowboy gets to thinking and asks his neighbor for a cow so he can double his herd. The other cowboys replies, “That’s fine by me partner, cuz then we’ll have the same number of cows?” How many cows does each cowboy own?

We’ll use A to represent the first cowboy and B for the second cowboy.

A + 1 = 2A, so A = 1.
A + 1 = B – 1, so B = 3.

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Aft to Fore and Fore to Aft

I run fore to aft on one side of a ship and aft to fore on the other. What am I?

The name of the ship.

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Move Your Digits

By moving one of the following digits, make the equation correct.

62 – 63 = 1

26 – 63 = 1
(26 = 2x2x2x2x2x2 = 64, ∴ 64 – 63 = 1)

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What Work is Never Finished?

What work can one never finish?

An autobiography. Unless you’re writing it in your death bed I suppose, but even then, how will you be able to record the time of death?

Posted in Riddles

Often Talked Of But Never Seen

Often talked of, never seen,
Ever coming, never been,
Daily looked for, never here,
Still approaching, coming near,
Thousands for it’s visit wait,
But alas for their fate,
Tho’ they expect me to appear,
They will never find me here.

Tomorrow.

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Cheese Made Backwards

What cheese is made backwards?

Edam cheese.

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