How many millisecond in 30 minutes?

Answer 1

30 x 60 = 1800 seconds x 1000 (milli) = 1,800,000 milliseconds

Answer 2

Given 60 seconds to the minute, 30 minutes contain 1,800 seconds;

given that there are 1,000 milliseconds in a second, there must be 1,800,000 milliseconds in 30 minutes.