Homework Help: math

Posted by Taylor on Monday, January 24, 2011 at 3:12pm.

It takes mary x hours to travel 100 kilometers. If she increases her speed by 5 kilometers per hour, the journey will take her 3 hours less time. Find x.

math - Reiny, Monday, January 24, 2011 at 3:34pm
her original speed be v
then vx = 100
her faster speed = v+5
(x-3)(v+5) = 100
xv + 5x - 3v - 15 = 100
100 + 5x - 3v = 115
5x - 3v = 15
v = (5x-15)/3

sub into 1st
x((5x-15)/3) = 100
5x^2 -15x = 300
x^2 - 3x - 60 = 0
I get x = 9.39 by using the formula (and v = 10.65)

check: (9.39)(10.65) = 100.0035
(6.39)(15.65) = 100.0035
YEAHH!

Answer this Question

Related Questions

Math - Traveling at r kilometers per hour for t hours, a driver will travel rt ...
ALGEBRA - If traveling at r kilometers per hour for t hours, a driver will ...
calculus - At noon, you and I start at the same place, and then you head east at...
math - Samantha’s speedometer reads in kilometers per hour. If the legal ...
math - Phil is making a 40-kilometer canoe trip. If he travels at 30 kilometers ...
math - Phil is making a 40-kilometer canoe trip. If he travels at 30 kilometers ...
math - Phil is making a 40-kilometer canoe trip. If he travels at 30 kilometers ...
math - Phil is making a 40-kilometer canoe trip. If he travels at 30 kilometers ...
MATH - Andrea made a car trip of 440 Kilometers. She averaged 54 Kilometers per ...
math - Andrea made a car trip of 440 Kilometers. She averaged 54 Kilometers per ...

For Further Reading

First Name:
School Subject:
Answer: