goahead

Let x be the height of the rectangle
16/10=y/x
y=1.6x

(1.6x)^2+x^2=19^2(Pyth. thm.)
3.56x^2=361
x=10.07(corr. to 2 decimal figure)
y=16.11(corr. to 2 decimal figure)

xy=10.07X16.11
area=162.22 square inch (corr. to 2 decimal figure)

goahead

Let x be the number of cows
Let y be the number of days they stay
Let z be the daily consumption of each cow
Let C be the growth rate of the grasses in each m^2
Let A be the area of the yard
therefore,
XYZ=A+AYC

10x20xZ=1200+24000C (1)
15x10xz=1200+12000C (2)

(2)x2
300z=2400+24000C (3)

(3)-(1)
100z=1200
      z=12
Let x=10,y=20,z=12 substitute (1)

10x20x12=1200+24000C
              C=0.05

When A=3600,x=75,C=0.05

75xYx12=3600+360x0.05xY
900Y=3600+180Y
720Y=3600
Y=5

therefore, 5 days.

goahead

If I am in examination,
I won't write it in detail^^

goahead

現已知20%的貨物是損壞。
現隨機抽取10個貨物樣本，找出最少有2個壞掉的貨物的機會率。(某數學書出的)