Phil wants to do well in his classes, so he is budgeting his time carefully to decide the number of classes he will take this year. For each class he expects to spend 3 34 hours a week working on homework, and additionally, two fifths of that time is planned to be spent on reviewing the reading material. If he has 23 hours available each week for homework and review, what is the best number of classes to take?

The table below shows the approximate masses of a dust particle and a grain of pollen. dust particle 0.000000778 g grain of pollen 0.00000000155 g the mass of a dust particle can be estimated and written in the form a × 10^b, where a = 8 and b = the mass of a grain of pollen can be estimated and written in the form a × 10^b, where a = 2 and b = based on the estimates, the mass of a dust particle is approximately blank times larger than the mass of a grain of pollen.