Working alone, Mary can pave a driveway in 3 hours and Hillary can pave the same driveway in 6 hours. When they work together, Mary thrives on teamwork so her rate increases by 10%, but Hillary becomes distracted and her rate decreases by 20%. If they both work together, how many hours will it take to pave the driveway?	Answers:
A) 2 hours	B) 4 hours	C) 5 hours	D) 6 hours	E) 7 hours
Initial working rates:   Mary = 1/3 per hour   Hillary = 1/6 per hour   Rate when working together:   Mary = 1/3 + (1/10*1/3) = 3/8 per hour   Hillary = 1/6 - (1/5*1/6) = 2/15 per hour   Together they work 3/8 + 2/15 = 1/2 per hour   So they will need 2 hours to complete the driveway. The correct answer is 2 hours.
<result>A</result>
Working alone, Mary can pave a driveway in 3 hours and Hillary can pave the same driveway in 6 hours. When they work together, Mary thrives on teamwork so her rate increases by 10%, but Hillary becomes distracted and her rate decreases by 20%. If they both work together, how many hours will it take to pave the driveway?