Cows on a farm

Question

The number of cows on a farm increased by 60. Because of better food, the amount of milk from each cow went up from 12.8 liters per day to 15 liters per day on the average. How many cows are on the farm now if the farmer gets 1340 liters of milk more per day?

Answer 1

The number of cows at begining =n

 liters of milk from n cows= m =12.8n
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number of cows increased by 60

number of cows = n+60

 liters of milk from n+60 cows = 15(n+60)

 

farmer gets 1340 liters of milk more per day

     

  m+1340 = 15(n+60)

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so we got 2 equation

 

m=12.8n                     ________ eq 1

m+1340 =15(n+60) ________eq 2

 

substitute m=12.8n in eq 2

12.8n +1340 =15(n+60)

12.8n +1340 =15n+900

2.2 n =440

n=200

n+60=200+60=260

 

so now in the farm 260 cows