**Egg equation**

If a hen and a half lay an egg and a half in a day and a half, how many eggs will half a dozen hens lay in half a dozen days?

**Answer**

Two dozen. If you increase both the number of hens and the amount of time available four-fold, the number of eggs increases 16 times. 16 x 1.5 = 24. If math riddles aren’t your thing, try solving these tricky detective riddles.

**Answer**

There are 47 cards.

If your favorite riddles don’t involve arithmetic, try solving these riddles for kids!

**Knight moves**

I have a calculator that can display ten digits. How many different ten-digit numbers can I type using just the 0-9 keys once each, and moving from one keypress to the next using the knight’s move in chess? (In chess, the knight move in an L-shape – one square up and two across, two squares down and one across, two squares up and one across, and other like combinations)

**Answer **

You can form the numbers 5034927618 and 5038167294. You can also form their reverses: 8167294305 and 4927618305. Hence four different numbers can be made. The key point is to realize that the number must start or end on the ‘5’ key, followed/preceded by the ‘0’ key, otherwise, there is no way of using all ten keys during the route. Only 2 percent of people can solve Einstein’s Riddle. Can you?

**Two by two **

You know 2 + 2 comes to the same as 2 x 2. Now find a set of three different whole numbers whose sum is equal to their total when multiplied.

**Answer **

The three different whole numbers whose sum is equal to their total when multiplied are 1, 2, and 3.

**Apple harvest**

Mrs. Jones was very proud of her apple tree. One autumn, after harvesting her apples, she called her three sons together. “Here are 150 apples,” she said. “I want you to take them to the market tomorrow and sell them for me.” She gave Paul 15 apples, Nick 50, and Ben 85. “Your job,” added Mrs. Jones, “is to sell the apples in such a way that each of you brings home the same amount of money.” How do they do it?

**Answer**

The first buyer purchases 12 dozen apples at $1 per dozen. Paul sells him one dozen and has three apples left; Nick sells him four-dozen and has two apples left; and Ben sells him seven-dozen and has one apple left. Then a second buyer comes along and buys all their remaining apples for $3 apiece. The three brothers head home with $10 each.

**Answer**

The answer to this math riddle is 21. You probably just guessed to answer this math riddle, which is fine, but you can also work it out algebraically. The two-digit number ab stands for 10a + b since the first digit represents 10s and the second represents units. If 10a + b = 7(a + b), then 10a + b = 7a + 7b, and so 3a = 6b, or, more simply, a = 2b. That is, the second digit must be twice the first. The smallest such number is 21.

**Lunch money**

John noticed that the amount he was paying for his lunch was a rearrangement of the digits of the amount of money he had in his pocket, and that the money he had left over was yet another rearrangement of the same three digits! How much money did John start with?

**Answer**

John started with $9.54. The money can be written with just three digits—so it must be between $1.01 and $9.99. Trial and error shows that there is only one set of numbers that fit this question: $9.54 = $4.59 + $4.95. If you can solve these math riddles easily, you’ll want to try your hand at what an MIT professor called the “hardest logic puzzle ever.”

**Answer**

The farmer has 3 sheep, 2 goats, 1 horse. Adding 3, 4, and 5, in this case, gives twice the number of animals, so there must be six animals altogether. Here are some genius math tricks you’ll wish you’d known all along.

**Brother puzzle**

One brother says of his younger brother: “Two years ago, I was three times as old as my brother was. In three years’ time, I will be twice as old as my brother.” How old are they each now?

**Answer**

The elder is 17, the younger 7. Two years ago, they were 15 and 5 respectively, and in three years’ time, they will be 20 and 10. Can you pass this elementary school math test?

**Answer **

The answer is 86. When it is turned upside down and flipped, it becomes 98, which is 12 more than 86. If you were able to solve all of these math riddles, try your hand at some of the hardest riddles ever written.