10.1 Percent 587 The procedure for changing a number given as a percent to a decimal number is equivalent to moving the decimal point two places to the left and removing the percent sign. Another way to remember that is: Percent means per hundred (or to divide by 100). Example 3 Converting a Percent to a Decimal Number a) Change 35% to a decimal number. b) Change 69.8% to a decimal number. c) Change 1 2 % to a decimal number. Solution a) 35% 35 100 0.35. = = Thus, 35% 0.35. = b) 69.8% 69.8 100 0.698. = = Thus, 69.8% 0.698. = c) 1 2 % 0.5% 0.5 100 0.005. = = = Thus, 1 2 % 0.005. = 7 Now try Exercise 19 Example 4 Monthly Investing Jahmir makes a monthly investment of $300 into his retirement plan. Of this $300, he invests $180 in stocks, $75 in bonds, and $45 in a money market account. Determine the percent that Jahmir invests monthly in stocks, in bonds, and in the money market account. Solution To determine the percent invested in stocks, we divide the amount of money invested in stocks, $180, by the total investment, $300. Percent invested in stocks 180 300 0.6 60% = = = We do a similar calculation to determine the percent invested in bonds and the percent invested in the money market account. Percent invested in bonds 75 300 0.25 25% Percent invested in the money market account 45 300 0.15 15% = = = = = = Note, that the sum of the percents, 60% 25% 15%, + + equals 100%. 7 Now try Exercise 35 Percent Change The percent increase or decrease, or percent change, over a period of time is determined by the formula: Percent Change Percent change amount in latest period amount in previous period amount in previous period 100% = ⎛ ⎝⎜ ⎞ ⎠⎟ − ⎛ ⎝⎜ ⎞ ⎠⎟ ×
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