GWD6第11和17

请教GWD6第11和17

Q11:

A certain business produced x rakes each month form November through February and shipped x/2 rakes at the beginning of each month from March through October. The business paid no storage costs for the rakes from November through February, but it paid storage costs of $0.10 per rake each month from March through October for the rakes that had not been shipped. In terms of x, what was the total storage cost, in dollars, that the business paid for the rakes for the 12 months form November through October?

A. 0.40x

B. 1.20x

C. 1.40x

D. 1.60x

E. 3.20x

Answer: c,why

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Q17:

A driver completed the first 20 miles of a 40-mile trip at an average speed of 50 miles per hour. At what average speed must the driver complete the remaining 20 miles to achieve an average speed of 60 miles per hour for the entire 40-mile trip? (Assume that the driver did not make any stops during the 40-mile trip.)

A. 65 mph

B. 68 mph

C. 70 mph

D. 75 mph

E. 80 mph

Answer: d ,why not c