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2. 3. 16 %. Warm Up 1. What is 35 increased by 8%? 2. What is the percent of decrease from 144 to 120? 3. What is 1500 decreased by 75%? 4. What is the percent of increase from 0.32 to 0.64?. 37.8. 375. 100%. Derive formulas for P, r & t. I = P r t Memorize.
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2 3 16 % Warm Up 1.What is 35 increased by 8%? 2. What is the percent of decrease from 144 to 120? 3. What is 1500 decreased by 75%? 4. What is the percent of increase from 0.32 to 0.64? 37.8 375 100%
Derive formulas for P, r & t I = Pr tMemorize P = I/ (r t)Divide both sides by r*t r = I/(P t)Divide both sides by P*t t = I/(Pr)Divide both sides by P*r
Solving for Interest Rate Mr. Johnson borrowed $8000 for 4 years to make home improvements. If he repaid a total of $10,320, at what interest rate did he borrow the money? P + I = AUse the formula. 8000 + I = 10,320 Substitute. I = 10,320 – 8000 = 2320 Subtract 8000 from both sides. He paid $2320 in interest. Use the amount of interest to find the interest rate.
1 4 2320 = rDivide both sides by 32,000. 32,000 Mr. Johnson borrowed the money at an annual rate of 7.25%, or 7 %. Example Continued I = Pr tUse the formula. 2320 = 8000 r4 Substitute. 2320 = 32,000 rSimplify. 0.0725 = r
Example: Solving for Time Mr. Mogi borrowed $9000 at an interest rate of 12% to make home improvements. If he repaid a total of $20,000, how long did he borrow the money? P + I = AUse the formula. 9000 + I = 20,000 Substitute. I = 20,000 – 9000 = 11,000 Subtract 9000 from both sides. He paid $11,000 in interest. Use the amount of interest to find the time in years.
11,000 = tDivide both sides by 1080. 1080 Time Example Continued I = PrtUse the formula. 11,000 = 9000 .12 tSubstitute. 11,000 = 1080 tSimplify. 10.18 = t Mr. Mogi borrowed the money for over 10 years.
Example 2: Solve for Time Nancy invested $6000 in a bond at a yearly rate of 3%. She earned $450 in interest. How long was the money invested? I = P r t Use the formula. 450 = 6000 0.03 tSubstitute values into the equation. 450 = 180t 2.5 = tSolve for t. The money was invested for 2.5 years, or 2 years and 6 months. Guided Practice 2
Example 3 TJ invested $4000 in a bond at a yearly rate of 2%. He earned $200 in interest. How long was the money invested? I = PrtUse the formula. 200 = 4000 0.02 t Substitute values into the equation. 200 = 80t 2.5 = tSolve for t. The money was invested for 2.5 years, or 2 years and 6 months. Guided Practice
Homework Instructions Complete ‘I=PxRxT’ Work Sheet Back Side Chart #1-7
Derive formulas for P, r & t I = Pr tMemorize P = I/ (r t)Divide both sides by r*t r = I/(P t)Divide both sides by P*t t = I/(Pr)Divide both sides by P*r