Explanation for Question 4 From the Math (No Calc) Section on the 2019 October Sat
Now looking at question number four, it tells us that the city transit bus 2 line charges $2 per adult and $1 per child 3 to ride the bus one way. Um, 4 so during that four hour shift, the bus driver collects $1,171 5 from 617 total writers. 6 And so we're looking for a systems of equations that would allow us to 7 determine the number of adult writers. So a capital a is adult and 8 child writer's capital C during this, 9 um, during this ride. And so the first thing that we should notice is 10 that there are going to be 617 writers and all of the writers are 11 going to be either adults or children. 12 So if I take the number of adult writers and I add it to 13 the number of child writers, I should get 617 because this 14 is the total number of writers. So we should be able to eliminate, 15 um, first off answer choice a, 16 because it says four times, 617. 17 Um, we should also be able to eliminate answer choice C because it just 18 has 117. And then finally we should be able to 19 eliminate, um, B because it has four times adult times child. 20 So just by looking at this, uh, one singular equation, 21 we can arrive at the correct answer of D it's. 22 The only equation that shows the correct number of total writers. 23 But as far as this first equation goes, 24 right, we know for every adult, it costs $2. 25 So if I do two times a, 26 that quantity would give me the total cost, 27 or I guess the total amount of money that the bus driver collected from 28 all the adult writers, right? Because every adult writer paid $2. 29 And if each child was $1, 30 we're essentially gonna do one times C, 31 which just shows up as C, right? And so since this quantity represents 32 the amount of money paid by the writers, 33 write $2 per adult, $1 per child. 34 If I add those together, I should get the total amount of money collected, 35 which was $1,171. 36 And we see that equation as well. And the answer choice D.