When buddy discovers the revolving door, he goes 4 complete revolutions in 11 seconds. How many times around would he go if he continued at this rate for a full minute

To figure out how many revolutions Buddy goes in 1 minute, (60 seconds) we can use proportions

4 revolutions/11 seconds = x revolutions/60 seconds

When we cross multiply, (multiplying one numerator by the other denominator, and vice versa for the other numerator) we get

240 = 11x

divide both sides by 11 to get

21.81 = x

or 21 complete revolutions