How many years from 1980 to 1990?

Answer 1

Leap years are those years which are divisible by 4 EXCEPT for centuries when the century must be divisible by 400; they occur every four years (except possible when a century ends).

As 1980 was a leap year, by subtracting 1980 from the current year, dividing by 4 and ignoring any remainder, the number of leap years after 1980 is found.

(1990 - 1980) ÷ 4 = 10 ÷ 4 = 2 r 2 → 2 leap years after 1980

→ There were 3 leap years in 1980-1990, which were 1980, 1984, 1988.

(These are also the years of the Summer Olympics.)