A survey at a concert showed that 1/25 of the audience came by car, 1/4 came by bus and the rest came by train. If there were 180 people who came by car, how many people came by train?
t = total number
180 = (1/25) t
t = 25 * 180
f is the fraction that came by train
1 = 1/25 + 1/4 + f
100/100 = 4/100 + 25/100 + f
f = 71/100
so 71/100 * 25 * 180 = 3195