TAILIEUCHUNG - SAT math essentials part 9

Tham khảo tài liệu 'sat math essentials part 9', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | PROBLEM SOLVING Practice Question If z is 2 of 85 what is 2 of z a. b. c. d. e. 17 Answer a. To solve break the problem into pieces. The first part says that z is 2 of 85. Let s translate z z z 100 x 85 50 x 85 85 50 17 10 z Now we know that z What is 2 of z 17 nr l 1 . 1 Tiỉl . ani r -1 T . 1 . -pý. The second part asks What is 2 of z Let s translate x Now let s solve for x when z y0 . Plug in the value of z. X z 100 -2- 100 1 000 _ X -17- x 10 x x Therefore is 2 of z. 155 ------------------------------------- PROBLEM SOLVING --------------------------------------------- Ratios A ratio is a comparison of two quantities measured in the same units. Ratios are represented with a colon or as a fraction x y ị 3 2 ị 9 a 9 Examples If a store sells apples and oranges at a ratio of 2 5 it means that for every two apples the store sells it sells 5 oranges. If the ratio of boys to girls in a school is 13 15 it means that for every 13 boys there are 15 girls. Ratio problems may ask you to determine the number of items in a group based on a ratio. You can use the concept of multiples to solve these problems. Example A box contains 90 buttons some blue and some white. The ratio of the number of blue to white buttons is 12 6. How many of each color button is in the box We know there is a ratio of 12 blue buttons to every 6 white buttons. This means that for every batch of 12 buttons in the box there is also a batch of 6 buttons. We also know there is a total of 90 buttons. This means that we must determine how many batches of blue and white buttons add up to a total of 90. So let s write an equation 12x 6x 90 where x is the number of batches of buttons 18x 90 x 5 So we know that there are 5 batches of buttons. Therefore there are 5 X 12 60 blue buttons and 5 X 6 30 white buttons. A proportion is an equality of two ratios. _L 2 6 7 35 a You can use proportions to solve ratio problems that ask you to determine how much of something is needed based .

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