Number Problems


Alphametics or Cryptarithems

The Stained Glass Window

Fours Puzzle

4 Dice

A*(B+C+D+E+F)

Switching Cards

Tomus's Books

Squaring the Square

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Three Digits

How Many Horses?

Dudeney's Tricks

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You see a design for a stained glass window which consists of a large circle and four small circles symmetrically placed within the larger as shown. The four smaller circles touch the outer circle and also meet at its centre.

The four "petals" labelled Y are in yellow glass, the four parts labelled B are in blue and the four parts labelled R are red.


We know there will be a total of 400 square centimetres of yellow glass in the window. Do you know how much blue glass is needed and how can you be sure?

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We need at least seven 4s to write the number 100 as a sum of numbers made up of the digit 4:
44 + 44 + 4 + 4 + 4 = 100

We need at least sixteen 4s to make 1,000:
444 + 444 + 44 + 44 + 4 + 4 + 4 + 4 + 4 + 4 = 1,000

Now, what is the smallest number of 4s we need to represent 1,000,000 in this way?

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Four identical dice are piled as shown in the picture. There are dots on the faces. How many dots are there on the bottom face of the bottom-most one? How can one guess? The sum of the opposite faces of real dice is *usually* 7. But you cannot rely on this fact in this problem.

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Professor Tomus has a great collection of books. The way Tomus numbers his book collection speaks volumes about his eccentricity:
8, 15, 22, 29, 36, 43... and so on up to 711117.

If these books were set out on one long shelf in numerical order, what would be the number on the spine of the middle volume?

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Garabaggio's Square is made up of a small number of squares fitted together without gaps or overlap to make a rectangular canvas measuring 176 cm by 177 cm. The side of each square measures a whole and different number of centimetres. The square at the top left measures 41 cm by 41 cm; the one at the bottom right measures 99 cm by 99 cm. Can you deduce the measurements of all the others?

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Divide 400 into 4 parts,
so that the first part multiplied by 4,
the second part divided by 4,
the third part plus 4,
and the fourth part minus 4,
all equal the same number.

 

Start calculating!

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405     Take a three-digit number and add it to another number made by rearranging the three digits of the number you took. The sum of these two numbers can, in its turn, also be made by rearranging the same three digits.

The example shown is inadmissible because we don't normally write a number with a zero at the beginning. There is another solution without this shortcoming. Can you find it?

045 +
450    

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B * ( A+C+D+E+F ) = 225
C * ( A+B+D+E+F ) = 301
D * ( A+B+C+E+F ) = 369
E * ( A+B+C+D+F ) = 400
F * ( A+B+C+D+E ) = 525
The next problem is:
Solve for A, B, C, D, E, and F.
Find integer values.

 
 

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A very rich farmer was getting bored and decided to count his horses. After counting them he discovered that the number of horses could be divided by 2,3,4,5,6,7,8,9 and 10. What is the MINIMUM number of horses this farmer has?

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  1. Deduct four thousand eleven hundred and a half from twelve thousand twelve hundred and twelve.
  2. Add 3 to 182 and make the total less than 20.
  3. What two numbers multiplied together produce seven?
  4. What three figures multiplied by five will make six?
  5. If five times four are 33, what is the fourth of 20?
  6. Find a fraction whose numerator is less than its denominator, but when turned upside down, remains the same value.
  7. Express with three equal digits 24. Can you do it for all nine digits?

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Imagine that below are laid out two rows of cards with numbers written on them. Now in how many ways and can you interchange cards from one row to the other to make the total of both rows the same?
The answer that use the fewest moves is best.

17, 15, 14, 18, 20

11, 12, 10, 13, 19

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