prep 1 32 難題....

Kath1985

32.2818-!-item-!-187;#058&002974

Al, Pablo, and Marsha shared the driving on a 1,500-mile trip.Which of the three drove the greatest distance on the trip?

(1)Al drove 1 hour longer than Pablo but at an average rate of 5 miles per hour slower than Pablo.

(2)Marsha drove 9 hours and averaged 50 miles per hour.

-------------------------------------------------------------------------------------------------------------------------------【
答案】E

Ａ	Ｐ	Ｍ	三人加總距離
時間＊速率	時間＊速率	時間＊速率
ａ＊ｂ	ｃ＊ｄ	ｅ＊ｆ	１５００
（ｃ－５）(d+１）	ｃ＊ｄ	450

為何答案不能是C  合併以後 A+P = 1050  和A一定比M大, 再由隱含條件( c-5)(d+1) 可知 c多減了5  乘積一定比 ｃ＊ｄ小  所以 一定是 P最大呀