Explanation for Question 37 From the Math (Calc) Section on the Official Sat Practice Test 6
Question 37 reads Jeremy deposited X dollars in his investment 2 account on January 1st, 2001, 3 the amount of money in the account doubled each year until Jeremy had $480 4 in his investment account on January 1st, 2005. 5 What is the value of X? 6 Okay. So one way to do this is to just write out the years 7 that were given. So we know that there's 2001, 8 2002, 2003, 9 2004 and 2005. 10 And we're trying to find X X being the amount that he deposited in 11 2001, we know that in 2005, 12 he had $480 in his bank account. 13 We can work sequentially backward to find out the value of X and find 14 out what he had in 2001 on the knowledge that the money in his 15 account doubled each year. So let's do 480 divided 16 by two to find out how much he had in 2004. 17 That's going to get us to two 40. 18 So this is just divided by two and do the same thing from 2004 19 to 2003, we'll divide it by two. 20 And that gets us to one 20, again, 21 divided by two. We now have 60 in 2002, 22 and one last time divide by two. 23 Well, we see that he has $30 in 2001. 24 So X is equal to 30.