instruction:
In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
question:
Problem: noelle walks from point a to point b at an average speed of 6 kilometers per hour . at what speed , in kilometers per hour , must noelle walk from point b to point a so that her average speed for the entire trip is 7 kilometers per hour ? 
Options: a ) 6.75 , b ) 7 , c ) 7.25 , d ) 7.5 , e ) 8.4
answer:
e


question:
Problem: the sector of a circle has radius of 21 cm and central angle 180 o . find its perimeter ? 
Options: a ) 91.5 , b ) 92 , c ) 108 , d ) 94 , e ) 95
answer:
c


question:
Problem: brenda and sally run in opposite direction on a circular track , starting at diametrically opposite points . they first meet after brenda has run 100 meters . they next meet after sally has run 100 meters past their first meeting point . each girl runs at a constant speed . what is the length of the track in meters ? 
Options: a ) 250 , b ) 300 , c ) 350 , d ) 400 , e ) 500
answer:

b