Some days, math goes very slowly around here. It's not that it's hard, but some drill problems can take a looooooooong time, partly because someone doesn't want to do it.
So I will occasionally use a trick that I read by Well Trained Mind author Susan Wise Bauer (it was either in the book or on a forum; can't remember).
Bite-size yummy treats.
I will put a bowl of treats on the table in front of the math student and allow one piece per problem finished. This really encourages faster work, and it takes the drudgery out of math problems.
Some treats we use are:
Sometimes my kids will count out the problems they have assigned and then count out their treats ahead of time. Then they will save them up until the entire math lesson is finished. Other times they will eat one after each problem.