Hi bildy!!!
Situation #1:
If we call T the total amount of pizzas delivered by Andrew we have
for the first delivery:
He deliver 1/6*T and then remains 5/6*T to deliver.
Second delivery:
Deliver 1/5*(5/6*T))=1/6*T , then remains 4/6*T to deliver.
Third delivery:
Deliver 1/4*(4/6*T)=1/6*T , then remains 3/6*T to deliver.
Fourth delivery:
Deliver 1/3*(3/6*T)=1/6*T , then remains 2/6*T to deliver.
Fifth delivery:
Deliver 1/2*(2/6*T)=1/6*T , then remains 1/6*T to deliver.
For the last delivery he has 5 pizzas, then
1/6*T = 5 ==> T = 5*6 = 30 pizzas.
Andrew begun with 30 pizzas.
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Situation #2:
Here I must work inthe way that I interpreted the problem, the
problemīs statement is a little obscure; but if we consider the the
two rivers as the coordinates axis x and y of the plane ( axis y for
the north to south river and axis x for the east to west river). The
origin is the point where the two rivers are crossed (the intersection
of the x- and y-axis), and the northeast quadrant is the first
quadrant of the plane (where x and y are both positive).
Trail A:
It starts at the point (0,300) and ends in the point (400,0).
Here we can follow to ways to determine the trail A, we can use the
Slope y-intercept form or the Two point form.
-Slope y-intercept:
y = m x + b, if m is finite.
When x = 0 , y = 300 and y = b, then b = 300.
When y = 0 , x = 400 and m = -b/x = -300/400 = -3/4.
Then the equation for the line containing the trail A is y = -3/4 x +
300 .
-Two point form:
Given two points, P1=(x1,y1) and P2=(x2,y2), the equation of the line
that contains the two points is:
(x-x1)(y2-y1) = (y-y1)(x2-x1)
Here P1=(0,300) and P2=(400,0) , then:
(x-0)(0-300) = (y-300)(400-0) ==> -300 x = 400 (y-300) ==> y-300 =
-300/400 x
==> y = -3/4 x + 300 .
The trail A comprises only the segment between P1 and P2,
such is for 0 =< x =< 400 .
-----------------------------------
Trail B:
Here we have a point P =(0,100) and (in some way) the slope m.
Let the slope of the line be m, if the inclination of a line is alpha
then
tan(alpha)= m . from this definition it is easy to see if we know how
varies y due a variation of x or viceversa that m = (variation of
y)/(variation of x);
in this case when we move 3 meters to the north (variation of y) we
move also 7 meters to the east (variation of x), then:
m = 3/7 .
We can use the -Slope y-intercept form:
y = m x + b, when x = 0 y = 100 and y = b , then b = 100.
So
y = 3/7 x + 100 .
Or we can use the Point slope form:
y - y1 = m(x-x1), if m is finite.
In this case (x1,y1) = (0,100) and m = 3/7 , then:
y - 100 = 3/7 (x - 0) = 3/7 x ==> y = 3/7 x + 100 .
Now we know when the trail starts (when x=0), but not when it ends.
It happens when the line meets the trail A, it is when both trail A
and trail B equations are satisfied:
-3/4 x + 300 = 3/7 x + 100 ==> 3/7 x + 3/4 x = 300-100 = 200 , then
33/28 x = 200 ==> x = 5600/33 ,
y = 3/7 x + 100 = 3/7 5600/33 + 100 = 800/11 + 100 = 1900/11 .
The meeting point is (5600/33,1900/11).
And the equation for the trail B is:
y = 3/7 x + 100 0 =< x =< 5600/33 .
-------------------------------
Trail C:
First of all we must calculate the area K in the northeast quadrant
that is south of both trail A and Trail B:
We have a plygon whose vertices are:
P1 = (0,0) origin
P2 = (0,100) start point of trail B
P3 = (5600/33,1900/11) meeting point of trails A and B [aprox
=(169.7,172.7)]
P4 = (400,0) end of trail A
We can use the expression:
The area of a polygon whose vertices are P1, P2, .., Pn is
K = [(x1y2 + x2y3 + x3y4 + ... + xny1) - (x2y1 + x3y2 + x4y3 + ... +
x1yn)]/2
and we have K = 1,420,000/33 .
Now we know that one of the possibilities for the trail C will form a
triangle whose vertices are the origin, the meeting point of trails C
and trail A and the end of trail A. We will work with this, if we get
an answer here, the problem is solved.
The area T of this triangle will be:
T = K/2 and
T = Base * High / 2 = 400 * H / 2
then
400*H = K ==> H = K/400 = (1,420,000/33)/400 = 3550/33 .
The high of this triangle is the y-axis value of the meeting point of
this trail with the trail A. The value obteined is less than the
y-axis value of the meeting point of the trails A and B, then this
trail is the correct one (that means the trail C donīt meet trail B
and the figure of the triangle used is correct, in other case, the
polygon is a quadrilateral).
Now we have the y-axis value of the meeting point of trails A and C,
then the x-axis value can be calculated using the equation of the
trail A:
3550/33 = -3/4 x + 300 ==> 3/4 x = -3550/33 + 9900/33 = 6350/33 ==>
x = 25400/99
The meeting point of trails A and C is (25400/99,3550/33).
We need to find the equation of trail C. We have two points, the
origin and the meeting point with trail A.
We can use the Two point form:
(x-x1)(y2-y1) = (y-y1)(x2-x1)
(x-0)(3550/33-0) = (y-0)(25400/99-0) then
3550/33 x = 25400/99 y then
y = 3550/33 . 99/25400 x = 213/508 x
The equation for trail C is:
y = 213/508 x 0 =< x =< 25400/99
-----------------------------------------
You will find useful the following page:
"Analytic Geometry Formulas" from DrMath.com:
http://drmath.com/dr.math/faq/formulas/faq.ag2.html
It is not possible to post a math graph here, but i think that the
explanations lead you to do the graph by yourself easily. If you still
have troubles with this, please let me know and I will try to find a
way to made the graphs availables to you.
I hope this helps you. Remember that if you think that the problem was
misunderstood by me, there are missing points, or need a clarification
please post a request for an answer clarification. I will be glad to
respond your requests. Please also let me know how this answer works,
and consider the fact that it be possible to find errors in
calculations (I checked them but...)but the most important thing here
is the showing of the way to solve the problems.
Best regards.
livioflores-ga |