Students participating in Dance from class VII is what percent of students participating in play from class IX.

Required ratio

$= frac{{frac{{10}}{{100}} imes 400}}{{frac{{12}}{{100}} imes 250}} imes 100$

$= frac{{10 imes 400}}{{12 imes 250}} imes 100 = 133frac{1}{3}{ m{\% }}$