Math Riddles

These Math Riddles are based on math concepts and can be solved with a bit of math and logic. These fun riddles can surely give you a tough time.

Row of Soldiers

There is a row of soldiers that is 1km in length and they walk with a constant speed in a straight line, in one direction.

All the way at the end walks a messenger. He has to bring a message to the captain walking all the way at the beginning of the row.

The messenger starts walking past the soldiers and immediately turns around when arriving at the captain and walks back to the end of the row. When the messenger is back at the end, the whole group of soldiers have traveled a distance of 1 km.

The soldiers and captain are walking at the same constant speed. The messenger (walking faster then the soldiers) is also walking a a constant speed.

You don’t know anything about time or speed. How far did the messenger travel from the end of the row to the beginning and back?

Riddle Answer

Cheryl Birthday

Albert and Bernard became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates.

May 15      May 16      May 19
June 17     June 18
July 14     July 16
Aug 14      Aug 15      Aug 17

Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.

Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too.
Bernard: At first I don’t know when Cheryl’s birthday is, but I know now.
Albert: Then I also know when Cheryl’s birthday is.

When is Cheryl’s birthday?

Riddle Answer

10 Digit Number

Find a 10 digit number where the first digit (most significant digit) indicates how many zeros are in the number, the second digit indicates how many 1s are in the number etc. till the tenth digit which indicates how many 9s are in the number.

Riddle Answer

Delivering Grain on Time

A collective farm was due to deliver its quota of grain to the state authorities. The management of the Kolkhoz decided the trucks should arrive in the city at exactly 11:00 A.M.

If the trucks traveled at 30 miles per hour they would reach the city at ten, an hour early; at 20 miles an hour they would arrive at noon, an hour late.

How far is the Kolkhoz from the city, and how fast should the trucks travel to arrive at 11:00 A.M.?

Riddle Answer

Train to Dacha

Two schoolgirls were traveling from the city to a dacha (summer cottage) on an electric train.

“I notice,” one of the girls said, “that the dacha trains coming in the opposite direction pass us every 5 minutes. What do you think-how many dacha trains arrive in the city in an hour, given equal speeds in both directions?”

“Twelve, of course,” the other girl answered, “because 60 divided by 5 equals 12.”

The first girl did not agree. What do you think?

Riddle Answer