中一英文數學問題(20marks)－貨運百科

標題:

中一英文數學問題(20marks)

發問:

Last year,Mrs Chan's weight was 3 times of her son's weight. This year,her son's weight increases by 10% while her weight decreases by 10%. Mrs Chan is now 32 kg heavier than her son. Find Mrs Chan's weight last year.

最佳解答:

Let x be the weight of Mrs.Chan and y be the weight of her son last year respectively. x=3y - (1) x(1-10%)-32=y(1+10%) - (2) From (2) , x(0.9)-32=y(1.1) 0.9x-32=1.1y - (3) Subsititute (1) into (3) 0.9 (3y) - 32=1.1y 2.7y-32 +32=1.1y +32 (+32 on both side) 2.7y-1.1y=1.1y + 32 -1.1y (-1.1y on both side) 1.6y=32 y=20 (i.e. the weight of her son last year was 20 KG) x=3(20) x=60 So, Mrs Chan's weight last year is 60 KG. by Jeffrey http://cytc-jeffrey.blogspot.com/

其他解答:

Let x be the weight of Mrs.Chan last year and y be the weught of her son last year x=3y - (1) x(1-10%)-32=y(1+10%) - (2) (2) - x(0.9)-32=y(1.1) 0.9x-32=1.1y - (3) Subsititute (1) into (3) 0.9x-32=1.1y 0.9(3y)-32=1.1y 2.7y-32=1.1y 2.7y-1.1y=32 1.6y=32 y=20 Substitute y=20 into (1) X=3(20) x=60 Mrs Chan's weight last year is 60 KG