# Mathematics exam 7

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## Mathematics exam 7

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## Nội dung Text: Mathematics exam 7

1. – DATA ANALYSIS, STATISTICS, AND PROBABILITY – C alculating Interest Example Kai invests $4,000 for nine months. Her invest- ment will pay 8%. How much money will she Interest is a fee paid for the use of someone else’s money. have at the end of nine months? If you put money in a savings account, you receive inter- Step 1: Write the rate as a decimal. 8% = 0.08 est from the bank. If you take out a loan, you pay inter- Step 2: Express the time as a fraction est to the lender. The amount of money you invest or by writing the length of time in months borrow is called the principal. The amount you repay is over 12 (the number of months in a year). the amount of the principal plus the interest. 9 months = 192 = 3 year The formula for simple interest is found on the for- 4 Step 3: Multiply. I = prt mula sheet in the GED. Simple interest is a percent of the =$4,000 × 0.08 × 3 principal multiplied by the length of the loan: 4 = $180 Interest = principal × rate × time Kai will earn$180 in interest. Sometimes, it may be easier to use the letters of each P robability as variables: Probability is expressed as a fraction and measures the I = prt likelihood that a speciﬁc event will occur. To ﬁnd the probability of a speciﬁc outcome, use this formula: Example Michelle borrows $2,500 from her uncle for Number of speciﬁc outcomes Probability of an event = three years at 6% simple interest. How much Total number of possible outcomes interest will she pay on the loan? Step 1: Write the interest as a Example decimal. 6% = 0.06 If a bag contains 5 blue marbles, 3 red marbles, Step 2: Substitute the known and 6 green marbles, ﬁnd the probability of values in the formula I = prt selecting a red marble: =$2,500 × 0.06 × 3 and multiply. Probability of an event = = $450 Number of speciﬁc outcomes Total number of possible outcomes Michelle will pay$450 in interest. 3 = 5+3+6 Some problems will ask you to ﬁnd the amount that Therefore, the probability of selecting a red marble is 134 . will be paid back from a loan. This adds an additional step to problems of interest. In the previous example, Michelle will owe $450 in interest at the end of three Helpful Hints about Probability years. However, it is important to remember that she will If an event is certain to occur, the probability is 1. ■ pay back the$450 in interest as well as the principal, If an event is certain not to occur (impossible), ■ $2,500. Therefore, she will pay her uncle$2,500 + $450 the probability is 0. =$2,950. If you know the probability of all other events ■ In a simple interest problem, the rate is an annual, or occurring, you can ﬁnd the probability of the yearly, rate. Therefore, the time must also be expressed in remaining event by adding the known probabili- years. ties together and subtracting their total from 1. 420