Grass in lawn grows equally thick and in a uniform rate. It takes 24 days for 70 cows and 60 days for 30 cows to eat the whole of the grass. How many cows are needed to eat the grass in 96 days.?	Choose the correct choice from the following answers:
A) 17
B) 18
C) 19
D) 20
E) 22
g= grass initially, r= rate at which grass grow/day, c= cow eat grass/day   g+24r=70*24= 
<gadget id="calculator">70*24</gadget>
<output>1_680</output>
1680c-----------1   g +60= 
<gadget id="calculator"> +60</gadget>
<output>60</output>
60*30= 
<gadget id="calculator">60*30</gadget>
<output>1_800</output>
1800c---------&gt;g=1800c-60r----------------2   by solving this 2 equation we have relation c=(3/10)r-------------3   g +96= 
<gadget id="calculator"> +96</gadget>
<output>96</output>
96nc=&gt;96nc=1800c-60r+96r=1800c+36r=1800c+120c=1920c   1800 +120= 
<gadget id="calculator">1800 +120</gadget>
<output>1_920</output>
1920c=&gt;n=20   ANSWER:20
<result>D</result>
Grass in lawn grows equally thick and in a uniform rate. It takes 24 days for 70 cows and 60 days for 30 cows to eat the whole of the grass. How many cows are needed to eat the grass in 96 days.?