Formulas

Example 1: If we invest P dollars at r percent for t years, the amount of simple interest I is given by the formula I =Prt. Find the amount of interest earned by $500 at 7% for 2 years.

Example 2: If we invest P dollars at a simple rate of r percent, then the amount A accumulated after t years is given by the formula A = P + Prt. If we invest $500 at 8%, how many years will it take to accumulate $600?

Example 3: Solve A = ½ bh for h

Example 4: Solve A = P + Prt for t.

Example 5: Solve A = P + Prt for P

Example 6: Solve A = ½ h(b₁ + b₂) for b₁

Example 7: Solve 2x – 5y = 7 for y in terms of x.

Example 8: Solve  for x.

Example 9: How long will it take $500 to double itself if we invest it at 8% simple interest?

Example 10: Mercedes starts jogging at 5 miles per hour. One-half hour later, Karen starts jogging on the same route at 7 miles per hour. How long will it take Karen to catch Mercedes?

Example 11: Two trains leave a city at the same time, one traveling east and the other traveling west. At the end of 9 ½ hours, they are 1292 miles apart. If the rate of the train traveling east is 8 miles per hour faster than the rate of the other train, find their rates.

Example 12: Bryan’s Pest Control stocks a 7% solution of insecticide for lawns and also a 15% solutions. How many gallons of each should be mixed to produce 40 gallons that is 12% insecticide?

Example 13: How many liters of pure alcohol must we add to 20 liters of a 40% solution to obtain a 60% solution?