Question

there are 60 cows in a field .some are brown and the rest are white. Two thirds of the brown cows are less than one year old. Three quarters of the white cows are less than one year old. There are twelve more brown cows than white cows. what fraction of all the cows are less than one year old?

Answer 1

Answer: 0.7

Explanation:

Let the number of white cows be x

Thus, the number of brown cows be (x+12)

Hence,

x+(x+12)=60

x+x+12=60

2x+12=60

2x+12-12=60-12

2x=48

Divide both parts of the equation by 2:

x=24 white cows

x+12=36 brown cows

The number of white cows are less than one year old:

`\displaystyle\\(3)/(4)(24)=\\\\(3(24))/(4)=\\\\ 3*6=\\\\ 18\ white\ cows`

The number of brown cows are less than one year old:

`\displaystyle\\(2)/(3)(36)=\\\\ (2(36))/(3)=\\\\ 2*12=\\\\24 \ brown \ cows`

The total number of cows are less than one year old:

`18+24=42\ cows`

Thus

Fraction of all the cows are less than one year old:

`\displaystyle\\(42)/(60)=\\\\(6*7)/(6*10)=\\\\(7)/(10) =\\\\ 0.7`