Can you do Test 6 section 4 number 37? I always miss this kind of question!
The best way to be sure you’re not missing the mark on a question like this is to actually list the years rather than just trying to capture everything in an equation. So say he starts with x dollars on January 1, 2001. You know his money doubles each year, so you can write the following.
January 1, 2001: x
January 1, 2002: 2x
January 1, 2003: 2(2x) = 4x
January 1, 2004: 2(4x) = 8x
January 1, 2005: 2(8x) = 16x
Of course, you know from the question that on January 1, 2005, Jeremy really had $480 in his account. Easy enough to solve from there:
16x = 480
x = 30
The unnecessarily complicated way to do this question is with an exponent formula. You know his money doubles every year for 4 years, so you can write:
Of course, that just simplifies to the same equation we just solved: 16x = 480.