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標題:

F 1 數學題

發問:

The total age of a father and his son is 55. Three years ago, the father was 6 times as old as his son. How old is the son now? Let X be the age of son , Y be age of father X + Y = 55

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最佳解答:

Let son and father is x and y years old now X + Y = 55...(1) 6(X - 3) = Y - 3...(2) (1) Sub. into (2) 6(X - 3) = 55 - X - 3 6X - 18 = 52 - X 7X = 70 X = 10 The son is 10 years old now

其他解答:

X+Y=55...(1) { 6(X-3)=Y-3...(2) (2) = 6X-18=Y-3 6X-Y =15(3) (3)+(1), 6X-Y =15 +) X+Y =55 ------------------------- 7X = 70 X = 10 ....(4) sub.(4) to (1), we have, (10)+Y=55 Y=45 so, the age of the son=10, and the age of the father +45. 希望幫到你^ ^