f.2 MAthz

周界 = 119 cm
長方形係有兩條邊長及兩條邊闊的.
即係話, 如果將長 = x, 闊 = y 的話, 咁我地可以立到條式:
2 (x + y) = 119

而家長同闊的比 = 10 : 7
我地將 x 同 y 改做 10z 同 7z
上面條式就會變成
2 ( 10z + 7z ) = 119
z = 3.5
所以長 = 3.5 x 10 = 35 (cm)
闊 = 3.5 x 7 = 24.5 (cm)

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Given Perimeter = 119 cm
Let x and y be the length and width of the rectangle, then
2 (x + y) = 119 ...(1)
Ratio of x:y = 10:7
Let x = 10z, y = 7z
Hence (1): 10z + 7z = 59.5
z = 3.5
therefore, x = 10 x 3.5 = 35 cm
y = 7 x 3.5 = 24.5 cm

let xcm and dcm are the length and the width of the file cover respectively.
4x=119
so x=29.75
x/d=10/7
d=7x/10
so d=20.825
hence the length is 29.75cm and the width is 20.825cm