Explanation for Question 1 From the Math (Calc) Section on the 2018 May Sat
Question one says a gravel company had 30 tons of gravel in stock 2 at the end of the day on Monday. So we know that on Monday, 3 there should be 30 tons of gravel on Tuesday, 4 the company shipped 10 tons of gravel and receive no deliveries. 5 So we know that on Tuesday, the number of gravel should decrease on 6 Wednesday. The company may know shipments and received a delivery of 20 tons 7 of gravel. So on Wednesday, 8 the gravel should increase on Thursday. 9 The company made no shipments and received no deliveries. 10 So on Thursday, it should stay the same. 11 And on Friday the companies ship 20 tons of gravel and received no deliveries. 12 So on Friday, it should decrease which of the following represents the number 13 of tons of gravel. The company had in stock at the end of each 14 day. So we know that this graph should start at 30 and then decrease 15 to Tuesday. And so there are two graphs that do that graph C 16 and D. So we can eliminate a and B already. 17 Then we know that on Wednesday, the amount should increase and both graphs increase. 18 So we're fine. On Thursday, 19 it should stay the same. And only this graph stays the same because C 20 decreases, which means that D is the correct answer.