Explanation for Question 20 From the Math (Calc) Section on the 2017 May Sat
Now for a number of 20, we're still using the same equation that was 2 above that. I wrote out here just for our convenience. 3 And the question asks, according to the equation, 4 approximately how many hours will it take the airplane to travel between the two 5 cities now to find out, 6 um, how much time it takes to travel the amount we 7 firstly, do realize what we're going to be replacing D with. 8 So we want to replace D with the amount that should be 9 there. If we're traveling from one city to another. 10 And if we go back the equation, 11 it, the question told us that the equation represents the distance 12 from the city and Ecuador, um, 13 hours after taking off from Pennsylvania. 14 So the distance from the city in Ecuador, 15 we want to be zero. We want D to be zero, 16 because that means that we are at the city in Ecuador. 17 If we start off, um, 2,565 miles 18 from the city in Ecuador, we start in Pennsylvania and we 19 fly all the way to Ecuador. 20 We should be zero miles away from Ecuador. 21 So D should be zero. And then we still have our equation 22 and all we need to do to solve for T um, 23 or the hours is isolated. 24 Leave it by itself. So I'm going to add 500 to, 25 to both sides. 26 And we have 500 T equals 2,565 27 to solve for T we divide both sides by 500. 28 And remember, you can use your calculator. 29 So we're doing 2,565 divided by 500, 30 which gives us T equals 5.13. 31 Now, obviously we don't see how to answer choice, but it does say approximately. 32 So we round, if we around this, 33 um, this would be about 5.1 or a D.