Explanation for Question 35 From the Math (Calc) Section on the Official Sat Practice Test 3
So now we're looking at question 35, which says it, 2 an online store received satisfaction ratings between zero and a hundred. 3 And the first 10 ratings, the average was 75. 4 Right? So for 10 ratings, we got an average of 75, 5 which means that the total amount of points altogether would have been 10 times 6 70, um, 10 readings. 7 So the average of 75, right? And so if I got my average, 8 we know that's equal to the sum, the total over the number, 9 right? And if that was 75 and we received 10, 10 then that means that the total number of points they received was 75 times 11 10, 750 points. 12 And then we need to know what is the least value the store can 13 receive on the 11th rating is still be able to have an average of 14 85 for the first 20 ratings. 15 Right? So if we're talking about 20 ratings, 16 then we have an average of 85, right. 17 Is equal to the sum over 20 ratings. 18 And we know that the sum of the first ratings was 750. 19 And so this, some that we're going to look at here is from ratings 20 11 to 20, right? 21 So let's figure out what that sum has to be. We'll multiply now, 22 85, 5 20. 23 That'll give us 1,700. We see that as equal to seven 50, 24 plus the sum of the second half of the ratings. 25 So we'll subtract seven 50 here. And we see that the sum of the 26 second half of the ratings is equal to 950. 27 Right? And so if we're looking at those 950, 28 and we think about, um, what our first, 29 uh, Le, or rather what our 11th rating could be, 30 if w...