Because... there are ten years in a decade - therefore there are ten decades in a century ! The prefix 'dec' means ten.
10 decades in 1 century
Century
The definition of a decade is 10 years. 8 decades would be 8 x 10 = 80 years.The definition of a century is 100 years.
There are 70 decades in 7 centuries. This is because each century consists of 10 decades, so when you multiply 7 centuries by 10 decades, you get a total of 70 decades.
One century is more than six decades. A decade is a period of 10 years, while a century is a period of 100 years. Therefore, one century is equal to 10 decades, making it a larger unit of time than six decades.