Angles on the clock

What is the acute angle between the hour and minute hands?

What time will it be when the same angle occurs for the first time after 10:10?

9-Digit Sum

 

 

Add or Multiply for the same result

 

1 + 2 + 3 = 1 x 2 x 3

How many more examples can you find like this?

2,2

1,1,2,4

1,1,1,2,5

...

Triangles with matchsticks

  

Hint: 3D

Digital Clock Puzzle 2

 

You have a digital clock with seconds. All digits must be different. With a valid time, what is the biggest number you can get when you sum the parts like this?

Time 12:34:56

12+34+56=102

Source

Digital Clock Puzzle

 

          What is the minimum number of segments?

Source

Weekly Math Challenge #3

 

Weekly Math Challenge #2

 

Divide into 6

 

 

Can you divide this figure into 6 identical shapes?

Zero Exponent

 

Target Number 15

  

 

8, 3, 8, 3

 This is asked me by a student. There are various versions of it on the Internet, however my student asked it the following way:

Percentage of Error

 

Al Biruni and Eratosthenes are two of the greatest mathematicians lived in the past. They both made some basic calculations to measure the circumference of the Earth.

 

Al Biruni estimated that the Earth has a circumference of 32 830 km.

Eratosthenes estimated that the Earth’s circumference was 39 375 km.

 

Of course, each of them used measurement units of their time. The numbers above are converted from their measurement systems to kilometers.

 

Accurate value of Earth’s circumference was calculated only in the last century.

The circumference of the Earth is 40 075 kilometers.

 

Can you find the percentage of error in Al Biruni and Eratosthenes’s calculations? Out of 100 percent, how close were they to the accurate length of the circumference?