To write a unit rate we have to find out, something per something. Here we will find out how many words per min. TO do this we will divide the amount of words (250) by the amount of minutes (5). Lets do it:-
250 ÷ 5 = 50
50 words per min.
CHECK OUR WORK:-
50 × 5 = 250
We were RIGHT!!
So, a unit rate for the situation "250 words in 5 minutes" is 50 words per min.
Hope I helped ya!! xD