The hot air balloon floated for 100 feet above ground.
The hot air balloon floated across 100 feet above ground.
The hot air balloon floated about 100 feet above ground.
I waited for her to finish doing her homework.
I waited across her to finish doing her homework.
I waited about her to finish doing her homework.
Look for the street before crossing.
Look across the street before crossing.
Look about the street before crossing.