In a primary six class,there are 25 and 15 boys. The school wishes to elect a headprefect from primary six. What is the probability that the headprefect elected is a girl?

There are a total of 40 students in the primary six class (25 girls + 15 boys).

The probability of electing a girl as headprefect is the number of girls divided by the total number of students:

Probability = Number of girls / Total number of students
Probability = 25 / 40
Probability = 5/8

Therefore, the probability that the headprefect elected is a girl is 5/8.