Answer:
0.1 milligrams
Step-by-step explanation:
We have been given that the number of milligrams, m, varies directly with the weight of the dog, w.
We know that two directly proportional quantities are in form
, where y is directly proportional with x and k is constant of proportionality.
Upon substituting our given variables in inversely proportion, we will get:

We have been given that veterinarian knows that a 50-pound dog gets 0.5 milligram of a certain medicine.
Let us find constant of proportionality using our given information.



So our required equation would be
.
Now, we will substitute
in our equation to solve for medicine needed for a 10-pound dog.


Therefore, the vet will give 0.1 milligrams of medicine to give a 10-pound dog.