Question

Each of the 30 boxes in a certain shipment with either 10 pounds or 20 pounds, and the average (arithmetic mean) weight of the boxes in the shipment is 18 pounds. If the average
weight of the boxes in the shipment is to be reduced to 14 pounds by removing some of the 20-pound boxes, how many 20-pound boxes must be removed?

A. 4
B. 6
C. 10
D. 20
E. 24


Please provide explanation justifying your answer.​

Answer 1

Answer:D. 20

Step-by-step explanation:

Answer 2

Answer:

D. 20

Step-by-step explanation:

x = 20 lb box:

20x + 10(30-x) = 18(30)

x = (540 - 300)/10

x = 24

If k = removed 20 lb box:

20(24-k)+ 10(6) = 14(6+24-k)

480 - 20k + 60 = 420 - 14k

540 - 420 = 6k

540 - 420 = 6k

k = 120/6 = 20