SOLUTION: Hi! I was wondering if you could help me with this problem please: A commercial jet can fly from San Francisco to Dallas in 3 hours. A private jet can make the same trip in 3 1/2 h

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Question 25847: Hi! I was wondering if you could help me with this problem please: A commercial jet can fly from San Francisco to Dallas in 3 hours. A private jet can make the same trip in 3 1/2 hours. If the two planes leave San Francisco at noon, after how many hours is the private jet twice as far from Dallas as the commercial jet?
Thanks! I appreciate it.
Answer by venugopalramana(3286) About Me  (Show Source):
You can put this solution on YOUR website!
Hi! I was wondering if you could help me with this problem please: A commercial jet can fly from San Francisco to Dallas in 3 hours.
LET THE SPEED OF COMMERCIAL JET (CJ)=S
IN 3 HRS IT CAN FLY =3S MILES = DISTANCE FROM SFC TO DALLAS
A private jet(PJ) can make the same trip in 3 1/2 hours.
SO SPEED OF PRIVATE JET =3S/3.5
If the two planes leave San Francisco at noon, after how many hours is the private jet twice as far from Dallas as the commercial jet?
LET US ASSUME THAT AFTER T HOURS the private jet WILL BE twice as far from Dallas as the commercial jet
DISTANCE TRAVELLED BY CJ IN T HRS = ST MILES..ITS DISTANCE FROM DALLAS
=3S-ST
DISTANCE TRAVELLED BY PJ IN T HRS =3ST/3.5 MILES...ITS DISTANCE FROM DALLAS
=3S-3ST/3.5
WE ARE GIVEN THAT
2(3S-ST)=3S-3ST/3.5
2(3-T)=3-3T/3.5
21-7T=10.5-3T
21-10.5=7T-3T=4T
10.5=4T
T=10.5/4=2.625 HRS.