Question 607247: Hello, For the life of me I can't figure out how to setup this problem. I've tried the work principle and others with no luck. I have a final coming up and this is one of five sample problems. I have worked the other four correctly but am stumped with this one. Help would be appreciated. Thank you, Rob Bob's tractor is just as fast as Lucy's.It Takes Bob 1 hour(s)more than it takes Lucy to drive to town. If Bob is 20 miles from town and Lucy is 10 miles from town, how long does it take Lucy to drive to town?
Found 2 solutions by lynnlo, ankor@dixie-net.com:
Answer by lynnlo(4176)   (Show Source):
Answer by ankor@dixie-net.com(22740)  (Show Source):
You can put this solution on YOUR website! Rob Bob's tractor is just as fast as Lucy's.
It Takes Bob 1 hour(s)more than it takes Lucy to drive to town.
If Bob is 20 miles from town and Lucy is 10 miles from town, how long does it take Lucy to drive to town?
:
Let t = time for L to make her trip
then
(t+1) = time for B to make his trip
:
Write a speed equation; speed = dist/time
:
speeds are equal therefore:
 = 
cross multiply, multiply the numerator on the left, by the denominator on the right,
Multiply the numerator on the right by the denominator on the left
20t = 10(t+1)
20t = 10t + 10
20t - 10t = 10
10t = 10
t = 1 hr for Lucy to drive to town, (2 hrs for Bob)
:
Cross multiplying is an easy way to solve an equation, but only can be used when there is a single fraction on either side of the equal sign
:
Check this, find the speeds
10/1 = 10 mph for Lucy
20/2 = 10 mph for Bob, like it says
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