The National Research Council recommends keeping 3:1 cooper to zinc ration in a horse's diet. if the horse is getting 420mg of zinc per day, how many milligrams of copper does the council recommend the horse to have?

1,260 mg of copper.

Step-by-step explanation:

This is because in a 3 to 1 ratio, the first number has to be 3 times the second number which is just multiplied by one. since zinc is the second number, it stays the same but the copper as to be 3 times the amount of zinc so 420 mg times 3 which equals 1,260.

Answer:140