Amy had 30 CDs

The mean playing time of these 30 CDs was 42 minutes.

Amy sold 5 of her CD.

The mean playing time of the 25 CDs left was 42.8 minutes.

**Calculate the mean playing time of 5 CDs that Amy sold.**

Guest May 7, 2015

#1**+8 **

Best Answer

Total time of all 30 can be written two ways:

25*42.8 + 5*m where m is mean time of the 5 CDs that were sold, and

30*42

So 25*42.8 + 5m = 30*42

See if you can find m from this.

.

Alan
May 7, 2015

#3**+5 **

Total playing time for all 30 is 30*42 = 1260 minutes

Total playing time for 25 left is $${\mathtt{25}}{\mathtt{\,\times\,}}{\mathtt{42.8}} = {\mathtt{1\,070}}$$

Total playing time for the 5 gone is $${\mathtt{1\,260}}{\mathtt{\,-\,}}{\mathtt{1\,070}} = {\mathtt{190}}$$

Average playing time for the 5 is $${\frac{{\mathtt{190}}}{{\mathtt{5}}}} = {\mathtt{38}}$$ minutes

Melody
May 8, 2015