[OK] Privacy Policy  -  Terms & Conditions  -  See DetailsWe use cookies to personalise content and ads. We also share information about your use of our site with our advertising partners who may combine it with other information you've provided to them or they've collected from your use of their services.

Puzzle Details

What 5 digit number am I thinking of.

• It has two prime digits.
• Digit 3 is the highest digit.
• Digit 2 is lowest digit.
• Digit 1 is higher than the sum of digits 4 and 5.
• Digit 5 is half of digit 4.
• Digit 1 is one smaller than digit 3.
• Digit 5 is between digit 2 and digit 1
• There are no duplicates and the digit 0 doesn't appear.
Don't forget that 1 isn't prime.

[Ref: ZVHE] © Kevin Stone

The number can be represented as:

_ _ _ _ _

Since digit 5 is half of digit 4 we have four possibilities:

_ _ _ 2 1
_ _ _ 4 2
_ _ _ 6 3
_ _ _ 8 4

But since digit 1 is higher than the sum of digit 4 and digit 5 we can eliminate two possibilities leaving:

_ _ _ 2 1
_ _ _ 4 2

Since digit 5 is between digit 2 and digit 1, we can eliminate _ _ _ 2 1, leaving:

_ _ _ 4 2

Since digit 1 must be higher than the sum of digit 4 and digit 5 we have three possibilities:

7 _ _ 4 2
8 _ _ 4 2
9 _ _ 4 2

But digit 1 is 1 smaller than digit 3 we can eliminate 9 _ _ 4 2, leaving

7 _ 8 4 2
8 _ 9 4 2

Since digit 2 is the lowest number, it must be 1:

7 1 8 4 2
8 1 9 4 2

The answer has exactly 2 prime digits, which only leaves

7 1 8 4 2.

Our Favourite Illusions

 Shadow Illusion Are the squares A and B the same colour? Spinning Dancer Which way is the dancer spinning? Impossible Waterfall? Is the water flowing uphill in this impossible waterfall? The Butterfly A colourful butterfly?
 Duck Or Rabbit? Is this a duck or a rabbit? Hidden Faces Can you find his three daughters as well? Blind Spot An amazing demonstration of your blind spot. Impossible Prongs? Impossible prongs?
 What Am I? Can you tell what this is a picture of? Who Turned To? Who is missing? Same Eyes? Are her eyes the same colour? Parallel Cafe Wall Lines? Are the horizontal lines parallel?