Current location - Training Enrollment Network - Mathematics courses - Wangzai is a math student.
Wangzai is a math student.
Xiao Ning went 1 trip, and dad went four times.

And because Xiao Ning arrived at school after receiving the book in 10 minutes,

So for Xiao Ning, it's 50 minutes' journey from home to school.

So in the 40th minute, Dad caught up with Xiao Ning.

It took Dad 10 minutes to catch up with Xiao Ning.

So dad set out to chase Xiao Ning at 40- 10=30 minutes.