標題:
maths f.3
發問:
the grammar maybe wrong, but the meaning is the same: Peter has been driving for x hours at 40km/h and y hours at 60km/h(the distance is 1800km/h). Then he return to the starting point at the speed of 50km/h, 比之前所需的時間快2hours.find the value of x and y 聯立方程ans
最佳解答:
40x + 60y = 1800....(1) 50(x + y - 2) = 1800....(2) (1) becomes 2x + 3y = 90...(3) (2) becomes x + y - 2 = 36 x + y = 38...(4) (3) - (4)*2 : y = 90 - 38*2 y = 14 x = 38-14 = 24
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