Explanation for Question 14 From the Math (Calc) Section on the Official Sat Practice Test 9
Question 14 reads a company purchased a machine valued at $120,000. 2 The value of the machine depreciates by the same amount each year. 3 So that after 10 years, the value will be $30,000, 4 which of the following equations gives the value V of the machine in dollars 5 T years after it was purchased for teas between zero and 10 years. 6 All right. So we're trying to essentially convert this word problem, 7 convert. These, this paragraph that we're given into an expression, 8 we know that the initial value of the machine is $120,000. 9 So looking at our expression, we know that the value should equal $120,000 10 minus some term with this term being how much it depreciates. 11 So from that alone, we can eliminate answer choice. 12 Okay, now we're still left with B, 13 C and D. We know that it depreciates by the same amount 14 each year, so that after 10 years, the value will be $30,000. 15 One way to do this is by setting up in expression. 16 So like I said, we know that it's 120, 17 excuse me. We know that it's V is equal to $120,000 18 minus T times M with M being some slope. 19 We know that after 10 years, the value will be $30,000. 20 So let's plug that point in V is going to be equal to 30,000. 21 And we know that T is going to be equal to 10. 22 So let's go through and solve for M we have 30,000 23 minus 120,000, 24 which is equal to negative 90,000, 25 and that is equal to negative 10. And so let's divide 26 both sides by negative 10. And we're left with M is equal to 9...