國小數學…比例問題

設甲乙兩包糖的重量分別為 x 和 y

x/y = 4/1 ......................... (1)

(x-10)/(y+10) = 7/5 ........... (2)


由(1)得 x = 4y

用 x = 4y 代入 (2) 得

(4y-10)/(y+10) = 7/5

5(4y-10) = 7(y+10)

20y - 50 = 7y+70

13y = 120

y = 9.23克

x = 4y

x = 36.9克

檢查 : x/y = 36.9/9.23 = 4.000

(x-10)/(y+10) = (36.9-10)/(9.23+10)=26.9/19.23 = 1.3988
7/5 = 1.4

設x為乙 則甲為4x
x+10/4x-10=5/7
20x*50=7x-70
13x=120
x=9.25
9.25*(1+4)=46.25(公克)