^ZERO IS YOUR BEST FRIEND IN REAL LIFE MATH.

   1) ROUND UP TO THE NEAREST 0
   if you're figuring out how much something costs.

   2) ROUND DOWN TO THE NEAREST 0
   if you're figuring out how much money you have.

   Now, percentages: Use your fingers, if you have 10.
   10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

   100 COUNT BY 10s
   10 20 30 40 50 60 70 80 90 100

   50 COUNT BY 5s
   5 10 15 20 25 30 35 40 45 50

   30 COUNT BY 3S
   3 6 9 12 15 18 21 24 27 30

   REAL LIFE MATH.^