12. A bus trip of 450 miles would have taken 1 hour less if the average speed S for the trip had been greater by 5 miles per hour. What was the average speed S, in miles per hour, for the trip?(A) 10
(B) 40
(C) 45
(D) 50
(E) 55
Answer: C
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(B) 40
(C) 45
(D) 50
(E) 55
Answer: C
Highlight 'Answer:' with your mouse, to see the answer choice.
Put your answers in comments section.
Solution:
ReplyDelete(450 / S) – (450 /(S+5)) = 1 Hr
450 ((S + 5 – S) / S(S+5)) = 1
2250 = S^2 + 5S
S^2 + 5S – 2250 = 0
(S-45) (S+50) = 0
S = 45 miles per hour or S = -50 miles per hour
S can’t be negative as they are in same direction.
Hence S = 45.