New SAT Math Workbook

24 solution there are 5 squares shaded out of 9 the

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Unformatted text preview: h can also be written 1 : 24. 24 Solution: There are 5 squares shaded out of 9. The ratio of the shaded portion to unshaded portion is 5 . 4 A proportion is a statement of equality between two ratios. The denominator of the first fraction and the numerator of the second are called the means of the proportion. The numerator of the first fraction and the denominator of the second are called the extremes. In solving a proportion, we use the theorem that states the product of the means is equal to the product of the extremes. We refer to this as cross multiplying. Example: Solve for x: Solution: Cross multiply. 6 x + 18 = 40 - 5 x 11x = 22 x=2 x +3 8- x = 5 6 Example: Solve for x: 4 : x = 9 : 18 Solution: Rewrite in fraction form. = x 18 Cross multiply. 9 x = 72 x =8 4 9 If you observe that the second fraction is equal to 1 1 , then the first must also be equal to . Therefore, the 2 2 missing denominator must be 8. Observation often saves valuable time. www.petersons.com 56 Chapter 4 Exercise 1 Work out each problem. Circle the letter that appears before your answer. 1. Find the ratio of 1 ft. 4 in. to 1 yd. (A) 1 : 3 (B) 2 : 9 (C) 4 : 9 (D) 3 : 5 (E) 5 : 12 A team won 25 games in a 40 game season. Find the ratio of games won to games lost. (A) (B) (C) (D) (E) 3. 5 8 3 8 3 5 5 3 3 2 4. Solve for x: 1 (A) 6 2 (B) 5 (C) 4 (D) 7 (E) 6 x + 1 28 = 8 32 2. 5. = Solve for y: 9 3 (A) 3 2y y -1 (B) (C) (D) (E) 1 3 9 15 9 4 4 9 In the proportion a : b = c : d, solve for d in terms of a, b and c. (A) (B) (C) (D) (E) ac b bc a ab c a bc bc d www.petersons.com Variation 57 2. DIRECT VARIATION Two quantities are said to vary directly if they change in the same direction. As the first increases, the second does also. As the first decreases, the second does also. For example, the distance you travel at a constant rate varies directly as the time spent traveling. The number of pounds of apples you buy varies directly as the amount of money you spend. The number of pounds of butter you use in a cookie recipe varies directly as the number of cups of sugar you use...
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This note was uploaded on 08/15/2010 for the course MATH a4d4 taught by Professor Colon during the Spring '10 term at Embry-Riddle FL/AZ.

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