Problem: Let r be the speed in miles per hour at which a wheel, 11 feet in circumference, travels. If the time for a complete rotation of the wheel is shortened by 41 of a second, the speed r is increased by 5 miles per hour. Then r is:
Answer Choices:
A. 9
B. 10
C. 1021
D. 11
E. 12
Solution:
r=t11⋅52801⋅3600 where t is given in seconds ∴t−1/411⋅52801⋅3600=t11⋅52801⋅3600+5
8t2−2t−3=(4t−3)(2t+1)=0,t=43,r=10