Bob wants to run a mile in the same time as his sister. If Bob’s time for a mile is currently 10 minutes 30 seconds and his sister’s time is currently 9 minutes 36 seconds, by what percent does Bob need to improve his time in order run a mile in the same time as his sister?  Choose the correct choice from the following answers.
A) 3 %
B) 5 %
C) 9 %
D) 10 %
E) 12 %

Rationale: "bob ' s time = 630 secs . his sis ' time = 576 secs . percent increase needed = ( 630 - 576 / 630 ) * 100 = 54 / 640 * 100 = 9 % . ans ( c ) ."
Answer: C