Explanation for Question 13 From the Math (Calc) Section on the Official Sat Practice Test 9
Question 13 reads a cargo helicopter delivers only 100 pound 2 packages and 120 pound packages for each delivery trip. 3 The helicopter must carry at least 10 packages. 4 And the total weight of the packages can be at most 1,100 pounds. 5 What is the maximum number of 120 pound packages that the helicopter can 6 carry per trip? Okay. 7 So to start with this problem, let's think about what it's asking us. 8 We know that the helicopter can carry both 100 and 120 pound packages. 9 So let's make an equation for the total weight of the helicopter. 10 So we have total weight is equal to 11 100 times, let's call the 100 pound packages, 12 the light packages, or make them variable. 13 L so 100 times owl plus 120 14 pound packages. Let's call those the heavy packages or H plus 15 120 times H. 16 So this expression is telling us the total weight, 17 and we know that the total weight of the packages can be at most 18 1,100 pounds. 19 So total weight max is equal to 20 1,100. We also know that 21 for each delivery trip, the helicopter must carry at least 10 packages. 22 So L plus H has to be greater than or equal to 10. 23 And these are our key expressions to solve the problem. 24 So let's figure out how many packages he is able 25 to carry, or how many, 120 pound packages he is able to carry to 26 do that we can set L plus H equals is 10, 27 because that is the minimum amount could we have Al plus H is equal 28 to 10 and let's solve, 29 or let's substitute for H let's say H is equal to,...