Question

Amy had 30 CDs. The mean playing time of these 30 CDs was 42 minutes. Amy sold 5 of her CDs. The mean playing time of the 25 CDs left was 42.8 minutes (b) Calculate the mean playing time of the 5 CDs that Amy sold.​

Answer 1

38 minutes

Explanation:

→ Find the total play time of 30 C's

30 × 42 = 1260

→ Find the total play time of 25 C's

25 × 42.8 = 1070

→ Subtract the 2 totals from each other

1260 - 1070 = 190

→ Divide it by 5

38 minutes

Answer 2

38 minutes

Explanation:

Because the mean playing time of the 30 CD's was 42 minutes, the total playtime was 42*30=1260 minutes.

Because the mean playing time of the 25 CD's left was 42.8 minutes, the total playtime was 42.8*25=1070 minutes.

So (1260 – 1070) = 190 minutes is the playtime of the 5 CD's Amy sold.

So the mean playtime of these 5 CD's was (190/5)=38 minutes.