math
posted by lisa on .
rudy went to the mall to spend some of his money he earned. he spent 1/3 of his money o n a new shirt. He then went to to the music store and bought a cd with 1/3 he had left. At dvds to go he bought a dvd with 1/3 of the money he had left. He stopped once more and bought a book with 1/3 of his remaining. Rudy came home with just $16.00left. how much did he start with?

Let M be the money he earned.
2/3 M is what he has left after new shirt.
2/3*2/3 M is what he has left after cd.
2/3*2/3*2/3M is what he has left after dvd.
16=(2/3)^4 M
M= 16*(3/2)^4=16*81/16=81
check that. 
how do you get back from 81/1 to 16/1

16*81/16... the 16/16 divides to 1, leaving 81

what's the final answer??

well youleft out the one third of the money from the book store