Question

A school district needs 3 teachers for every 70 children. They expect to have 14,700 children in the district next year. At this time, they have 612 teachers. How many more teachers are needed?

Answer 1

Three teachers are needed for 70 children, that is:
3 = 70..............  equation 1.
 For 14,700 children, Y number of teachers are needed, thus, we have
Y = 14,700...........equation 2.
3 = 70
Y = 14, 700.
Cross multiplying we give us,
3 * 14, 700/70 * Y.
44,100/70Y
Y = 630.
Thus, 630 teachers are needed to teach 14,700 children.
The district already have 612 teachers, so they need 630 - 612 = 18. 
So, the district needs 18 more teachers.