<p>I totally forgot how to do these kinds of problmes, its a grid in, can some one tell me how to solve this one and one's like these on the SAT?</p>
<p>It took Bob 1.5 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 the round trip was 10/3 hours, what was Bob's average speed in miles per hour on the way to the beach?</p>
<p>Ans: 30</p>
<p>If you know the formula RT=D, you're set:</p>
<p>Basically, create a simple equation. You know the total time is 10/3 hr, thus the time going to the beach and coming back = this value. Solve for T using the equation: T= D/R.</p>
<p>Each distance is 60 miles, but the rates vary so use a variable. For simplicity's sake, let's use x as Rate going home. 1.5x= rate driving to the beach.</p>
<p>Now, using T1 (time going) + T2 (coming back) = 10/3, rewrite these times using x.</p>
<p>T1= Distance/Rate= 60/1.5x
T2= D/R= 60/x</p>
<p>60/x + 60/1.5x = 10/3.</p>
<p>Solving for x yields 30 mph.</p>
<p>One More...</p>
<p>Points, L, M and N lie in a plane. If the distance between L and M is 4, and the distance between M and N is 9, which of the following could be the distance between L and N?</p>
<p>I. 5
II. 8
III. 13</p>
<p>A) I only
B) II only
C) III Only
D) I and III
E) I, II and III</p>
<p>Ans: E </p>
<p>I got 5 and 13 but to get 8 I tried the pythagoream theor. and got very close to 8, I believe it was ~8.06 or so but since it was not 8 I did not choose it...what should I do?</p>
<p>These problems can be tricky if your not used to D=RT questions. Took me a good 5 min to get it right lol.</p>
<p>Lets first set up the variables.
Lets say 1.5x is the time it takes to go to the beach, and y is the time it takes to get home.</p>
<p>1.5X=Y because 1.5 the time it takes to get to the beach then it takes to return.</p>
<p>X+Y= 10/3 becauses 10/3 is the total time, and X and Y gives us the total time back and forth.
We substitutute 1.5X for Y, yielding 1.5X+X= 10/3
Thus
2.5X=10/3
We want X, which is the way to the beach.
10/3 / 2.5 = X</p>
<p>X= 1.33333333</p>
<p>X is the time it takes to get to the beach. We want the way home, so simply subtract 1.3333333 from the total time which is 10/3 or 3.333333333</p>
<p>thus y = 2 </p>
<p>However, that only gives us the TIME, we want average SPEED.</p>
<p>D=RT</p>
<p>its 60 miles to get home and it took 2 hours.
60/2 = 30 MPH</p>
<p>Hope that helps!</p>
<p>^The distance can be 5 if the order of the points from left to right is N,L,M. The distance can be 13 if you swing the line segment MN all the way to the right so that the order is L,M,N. Now, as you're swinging the line segment MN, the distance between L and N goes from 5 (minimum) to 13 (maximum), so 8 is a possible distance.</p>
<p>Another way to imagine this is to think of a triangle. Now, it's not possible to have a triangle of side lengths 5,12, and 19, because the side length 19 is too long (even when 5 and 12 are lined up side by side, the most you can get is 17). Furthermore, a triangle of 5,6, and 12 won't work because the side length 12 is too long. But the triangle could have side lengths of 5,12, and 13. It can also have side lengths of 5,12,and 12, and 5,12, and 11. The length of the third side length just has to be more than 7 and less than 17.</p>
<p>If they lie in a line, then its not possible to get 8. If its a plane, 8.06 is still not a sufficient answer. Does anyone know how to tackle this prob?</p>
<p>So if it says "plane", then you can make it into a triangle?!</p>
<p>^ A plane is not the same as a line. A plane is like a flat piece of paper extended indefinitely.</p>
<p>to quix, if there are only 3 random points on a plane, the only thing that can be made is a triangle.</p>
<p>Ya, i thought a plane referred to a horizontal straight line lol. Oh deeeeeeeeeeeeeer.</p>
<p>Its fine. Its still summer</p>
<p>Use the triangle inequality. a + b > c</p>