SOLUTION: A man calculated that if his speed had been increased by 4km/h he would have completed his 48km journey 1 hour sooner.determine his speed.

Question 577439: A man calculated that if his speed had been increased by 4km/h he would have completed his 48km journey 1 hour sooner.determine his speed.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A man calculated that if his speed had been increased by 4km/h he would have completed his 48km journey 1 hour sooner.
determine his speed.
:
Let s = his speed
then
(s+4) = his faster speed
:
Write a time equation: time = dist/speed
:
normal time - faster time = 1 hr
- = 1
Multiply by s(s+4)
s(s+4)* - s(s+4)* = 1s(s+4)
cancel the denominators
48(s+4) - 48s = s^2 + 4s
48s + 192 - 48s = s^2 + 4s
0 = s^2 + 4s - 192 = 0
Factors to
(s-12)(s+16) = 0
the positive solution
s = 12 mph his speed
:
:
Check this by finding the actual times
48/12 = 4 hrs
48/16 = 3 hrs
---------------
diff is 1 hr

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