Three-fourths of the students at Bismarck High are less than 16 years old. If there are 1200 students at the school, how many of them are under 16?

A) 400

B) 600

C) 700

D) 900

So we want to know how many students at Bismarck High are under 16 if we know that 3/4 or 0.75 or 75% or 75/100 of them is under 16. And we know there are 1200 students. So lets see how many students is 75% out of 1200. (75/100) * 1200=900. So 900 students are under 16.