a) there's 1 ticket out of 250, so the answer is \(\boxed{\frac{1}{250}=0.4\%=0.004}\)

b) there's 10 tickets out of 250, so the answer is \(\boxed{\frac{1}{25}=4\%=0.04}\)

c) there's 25 tickets out of 250, so the answer is \(\boxed{\frac{1}{10}=10\%=0.1}\)

.