Explanation for Question 19 From the Math (Calc) Section on the Official Sat Practice Test 9
Question 19 reads that on Tuesday, 2 Jennifer will mix crunchy green cereal with super green cereal for her breakfast. 3 Super green cereal provides 240 calories per cup. 4 If total number of calories in one cup of Jennifer's mixture is 270. 5 How much super green cereal is in one cup of the mixture. 6 Okay. So we know that super green cereal is 7 240 calories per cup. 8 And we know that crunchy green cereal has 210 calories 9 per three fourths cup. So let's figure out how many cups 10 would or how many calories would be in one cup of crunchy green 11 cereal. So we have three fourths cup over 12 210 calories, and we can set this up as a ratio equals one cup 13 over X calories. We can cross multiply and we have three 14 fourths. X is equal to 210 and 210 15 divided by three fourths is going to be two 80. 16 So X is equal to two 80, meaning that there are 280 calories 17 per one cup of crunchy grain. 18 Let's call that CG cereal. 19 Now from there, we know that she has one copper. 20 We're trying to figure out the caloric intake of one cup of cereal. 21 So we can set that up as an expression. 22 We have 280 calories per cup, 23 times X cups of crunchy 24 green. So X will be the cups of crunchy grain. 25 Plus we have 270 calories per 26 cup times, 27 Y which is going to be the cups of super grain is equal to 28 200 and, or excuse me, 29 that should be 240 calories per cup is how many calories are in super 30 grain. And we know that the total calories per one cup 31 is 270 calori...