<p>It took Garth 1 1/2 times as long to drive to the beach as it took him to drive home. If the trip was 60 miles in each direction and the total driving time for round trip was 3 1/3 hours, what was Garth's average speed in miles per hour on the way to the beach?</p>
<p>Can i use xiggis method here? The 2 * r1 * r2 / r1 + r2</p>
<p>if so how? if not whats the fastest and easiest way to solve this?</p>
<p>Thanks guys</p>
<p>Btw man was cc shutdown yesterday? couldnt get on for hours</p>
<p>Why not use CyberShot's method?</p>
<p>The key piece of info they give you is that the total trip was 3 1/3 hrs, which we can write as 10/3.</p>
<p>It took him 1.5 hrs longer to get to the beach. By simple CyberShot-ean logic, this means we can ascribe a value for the time it took him to get there.</p>
<p>Since it took him 3/2 longer, we can say that whatever time it took him to come home, x, is 2/3 as big as what time it took him to get there, which is 3/2.</p>
<p>So, we write</p>
<p>x+3/2x= 10/3</p>
<p>Multiplying through by 6, we get </p>
<p>6x+9x=20</p>
<p>15x=20</p>
<p>x=4/3</p>
<p>Thus, it took him 4/3 of an hour to arrive at the beach and we know how far away the beach is, 60 mi.</p>
<p>We're left with 60/(4/3) which equals 3/4(60) or 45 mi/h.</p>
<p>:)</p>
<p>And yes, the site was down yesterday.</p>
<p>that would be right...if the answer was 45</p>
<p>too bad its 30 according to the book...:(</p>
<p>Oops, I made a careless error..</p>
<p>Once you I got 4/3, I meant to multiply by 3/2 because the time it takes to get there is that much greater.</p>
<p>So, (4/3)(3/2)= 6/3, or 2</p>
<p>Hence, 60/2= 30 mi/h which is your answer.</p>
<p>Sorry for the mix-up</p>
<p>t1, r1 - time, speed on the way to beach
t2, r2 - on the way back.</p>
<p>t1 = (3/2) t2
t1 / t2 = 3/2.
Splitting total time 10/3 hrs in 3:2 ratio
(6/3) : (4:3).
t1 = 6/3 = 2 hrs.
r1 = 60 mi / 2 hrs = 30 mi/hr</p>
<p>Let' verify this with the formula from xiggi.</p>
<p>Since t1 / t2 = 3/2
r1 / r2 = 2/3</p>
<p>Average speed
2 r1 r2 / (r1 + r2) = 120 / (3 1/3)
2 r1 r2 / (r1 + r2) = 36
r1 r2 = 18 r1 + 18 r2
divide both sides by r2
r1 = 18 r1 / r2 + 18
r1 = 18 (2/3) + 18
r1 = 30 mi/hr.
Same answer. xiggi must've been right :).</p>