Lisa Bell, Know Your Numbers

We all watch TV, but your kids are watching a lot of TV -- try 15,000 hours.

A new study says that between ages 2 and 17, your kids will watch about 15,000 hours of TV. That is equal to about three years of their waking lives.

Whether it is cartoons or docu-dramas, doctors say it is still eating up time the kids could be playing and getting exercise.

That 30 minutes a day of exercise you are supposed to get applies to kids, too. 

Thirty minutes a day means about 15 hours a month -- or about one-fifth of those 15,000 TV hours.