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The triangle enclosed by the line x+y=m and the coordinate axes is a right-angled triangle with legs parallel to the coordinate axes. Let's call the length of the horizontal leg of the triangle x, and the length of the vertical leg y. Then, the area of the triangle is:

A = (1/2)xy

We can use the equation of the line to express x and y in terms of m:

x + y = m

x = m - y

y = m - x

Substituting these expressions into the equation for the area, we get:

A = (1/2)(m - y)y

A = (1/2)(m - x)x

Combining these two expressions and simplifying, we get:

A = (1/2)(m - x)x = (1/2)(m - y)y

A = (1/2)(m^2 - xy)

2A = m^2 - xy

We know that the area of the triangle is 200 square units, so we can substitute that into the equation and solve for m:

2A = m^2 - xy

2(200) = m^2 - xy

400 = m^2 - xy

We need to find values of x and y that satisfy the equation x + y = m and the equation 400 = m^2 - xy. We can substitute x = m - y into the second equation to get:

400 = m^2 - x(m - x)

400 = m^2 - mx + x^2

Rearranging and factoring, we get:

x^2 - mx + (m^2 - 400) = 0

This is a quadratic equation in x. We can use the quadratic formula to solve for x:

x = [m ± sqrt(m^2 - 4(m^2 - 400))] / 2

x = [m ± sqrt(1600 - 3m^2)] / 2

For the triangle to be a right-angled triangle, one of the legs must have length 10 times larger than the other leg. Let's assume that the horizontal leg is 10 times larger than the vertical leg, so x = 10y. Substituting this into the equation above, we get:

10y = [m ± sqrt(1600 - 3m^2)] / 2

20y = m ± sqrt(1600 - 3m^2)

We know that y is a positive number, so we can take the positive root:

20y = m + sqrt(1600 - 3m^2)

Squaring both sides, we get:

400y^2 = m^2 + 1600 - 2m sqrt(1600 - 3m^2)

Rearranging, we get:

2m sqrt(1600 - 3m^2) = m^2 - 400y^2 + 1600

Squaring both sides again, we get:

4m^2 (1600 - 3m^2) = (m^2 - 400y^2 + 1600)^2

Expanding and simplifying, we get:

-3m^4 + 400m^2 - 1600y^2 = 0

This is a quadratic equation in m^2. We can use the quadratic formula to solve for m^2:

m^2 = [-(400) ± sqrt(400^2 - 4(-3)(-1600y^2))] / (-6)

m^2 = [200 ± 10sqrt(200 + 3y^2)] / 3

=[200 ± 388]/3

We need the positive root, m^2 = (200 + 388)/3 = 196.  Therefore, m = 14.

Mar 11, 2023
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Mar 11, 2023
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Let's denote the two points on the circle as A and B, and let's assume that A is fixed at the top of the circle (i.e., at the point (0,1)). We can then use polar coordinates to describe the position of point B on the circle. Let θ be the angle that the line segment AB makes with the positive x-axis, measured in radians.

We can then write the position of point B as (cos θ, sin θ), since it lies on the circle of radius 1 centered at the origin. Since we are choosing point B at random, the angle θ is uniformly distributed on the interval [0, 2π).

To find the probability that the distance between A and B is at most 1.5, we need to find the set of values of θ that satisfy this condition. The distance between A and B is given by the formula:

distance AB = sqrt((cos θ - 0)^2 + (sin θ - 1)^2) = sqrt(cos^2 θ + (sin θ - 1)^2)

So, the condition that the distance between A and B is at most 1.5 is equivalent to the inequality:

sqrt(cos^2 θ + (sin θ - 1)^2) ≤ 1.5

Squaring both sides and simplifying, we get:

cos^2 θ + (sin θ - 1)^2 ≤ 2.25

Expanding the second term and simplifying, we get:

sin^2 θ - 2sin θ + 2 ≤ 0

Using the quadratic formula to solve for sin θ, we get:

sin θ ≤ 1 ± sqrt(3) / 2

Since θ is uniformly distributed on the interval [0, 2π), the probability that sin θ satisfies this inequality is equal to the ratio of the length of the interval [0, 2π) for which sin θ satisfies this inequality to the length of the entire interval [0, 2π). The length of the interval [0, 2π) for which sin θ satisfies this inequality can be found by considering the two cases:

sin θ ≤ 1 + sqrt(3) / 2: In this case, we have:

0 ≤ θ ≤ pi/3 or 5pi/3 ≤ θ ≤ 2pi

The length of this interval is pi/3 + (2pi - 5pi/3) = 4pi/3.

sin θ ≤ 1 - sqrt(3) / 2: In this case, we have:

pi/3 ≤ θ ≤ 2pi/3 or 4pi/3 ≤ θ ≤ 5pi/3

The length of this interval is (2pi/3 - pi/3) + (5pi/3 - 4pi/3) = 2pi/3.

Therefore, the probability that the distance between A and B is at most 1.5 is:

 

(4pi/3 + 2pi/3) / 2pi = 1

So the probability that the distance between two randomly chosen points on the circle of radius 1 is at most 1.5 is 1 or 100%

Mar 11, 2023
Mar 10, 2023
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We can solve this problem using geometric probability. Let A be the area of triangle XYZ, which is (1/2)(12)(6) = 36. We can think of the point D as being chosen uniformly at random in the triangle XYZ. This means that any point in the triangle is equally likely to be chosen.

Let's consider the set of all possible points D that could be chosen. Since D can be any point in the triangle, this set is just the triangle XYZ itself. Let's call the set of all points within the triangle that make triangle XYD have area at most 20 as set S.

We want to find the probability that a randomly chosen point D is in set S. This probability is given by:

P(D in S) = (Area of S) / (Area of XYZ)

Let's find the area of S. We can think of S as being the region above line XY and below line DZ, where D is any point on line XY such that triangle XYD has area 20. Let's call the intersection of line XY and line DZ point E. Then triangle XYD has base 12 and height 20/12 = 5/3. This means that point D lies on a line parallel to YZ and 5/3 units above line XY. Let's call this line l.

The point E divides line YZ into two segments of length 2 and 4, since XY is perpendicular to YZ and XY = 12. Therefore, the distance from point E to line YZ is 2/3 of the length of YZ, or 4. We can use this information to find the equation of line l in slope-intercept form:

The slope of line l is -3/5 (since it is parallel to YZ and perpendicular to XY), and it passes through point (0, 5/3) (since it is 5/3 units above XY). Therefore, the equation of line l is:

y = (-3/5)x + 5/3

We want to find the x-coordinates of the points where line l intersects lines XY and DZ. Let's call these points F and G, respectively. To find the x-coordinate of point F, we plug in y = 0 into the equation of line l:

0 = (-3/5)x + 5/3

Solving for x, we get:

x = 5

Therefore, point F has coordinates (5, 0). To find the x-coordinate of point G, we plug in y = 6 into the equation of line l:

6 = (-3/5)x + 5/3

Solving for x, we get:

x = 19/3

Therefore, point G has coordinates (19/3, 6). The area of triangle XYD is (1/2)(12)(DF), where DF is the distance from point D to line XY. We want this area to be at most 20, so we have:

(1/2)(12)(DF) ≤ 20

Solving for DF, we get:

DF ≤ 10/3

This means that any point D on line l such that DF ≤ 10/3 will be in set S. We can find the x-coordinates of these points by solving the inequality:

(-3/5)x + 5/3 ≤ 10/3

Solving for x, we get:

x ≤ 25/3

Therefore, the set S is the region bounded by lines XY, DZ, and the line:

y = (-3/5)x + 5/3

in the triangle XYZ, where the x-coordinate of any point in this region is at most 25/3.

We can find the area of S by finding the area of the region bounded by lines XY, DZ, and the line y = (-3/5)x + 5/3 whose x-coordinate is at most 25/3. We can break this region into two triangles and a trapezoid. The area of the two triangles is:

(1/2)(12)(5/3) + (1/2)(25/3)(6-5/3) = 25/3

The area of the trapezoid is:

(1/2)(25/3 + 5)(5/3) = 100/9

Therefore, the area of S is:

25/3 + 100/9 = 275/27

Finally, we can find the probability that a randomly chosen point D is in set S by dividing the area of S by the area of XYZ:

P(D in S) = (275/27) / 36 = 275/972

Therefore, the probability that the area of triangle XYD is at most 20 is 275/972.

Mar 10, 2023
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We can solve this problem by using the Principle of Inclusion-Exclusion (PIE). We first count the total number of ways to seat the six children without any restrictions.

There are 6 choices for the first seat, 5 choices for the second seat (since one child has already been seated), and so on, for a total of 6! = 720 possible arrangements.

Next, we count the number of arrangements where at least one pair of siblings sit next to each other in the same row. We can choose one of the three pairs of siblings to sit together, and then there are 2 ways to arrange these siblings within the pair. There are 4 choices for the first seat in the row containing the pair, and then 3 choices for the second seat (since one child is already seated), for a total of 3 * 2 * 4 * 3 * 2 = 144 arrangements. However, we have overcounted the arrangements where two pairs of siblings sit together, so we need to subtract them off.

There are 3 ways to choose which two pairs of siblings sit together, and then there are 2 ways to arrange each pair within their respective row. There are 2 choices for the first seat in the row containing the first pair, and then 1 choice for the second seat (since the other child in that pair is already seated), and 2 choices for the first seat in the row containing the second pair, and then 1 choice for the second seat (since the other child in that pair is already seated), for a total of 3 * 2 * 2 * 1 * 2 * 1 = 24 arrangements.

However, we have subtracted too much, since there is one arrangement where all three pairs of siblings sit together in the same row that we have subtracted twice. There are 3! = 6 ways to arrange the three pairs within the row, and then 3! = 6 ways to arrange the rows, for a total of 6 * 6 = 36 arrangements.

Therefore, the number of arrangements where at least one pair of siblings sit together in the same row is 144 - 24 + 36 = 156.

Finally, we subtract this number from the total number of arrangements to get the number of arrangements where no pair of siblings sit together in the same row:

720 - 156 = 564.

Therefore, there are 564 ways to seat the three pairs of siblings from different families in two rows of three chairs, if siblings may sit next to each other in the same row, but no child may sit directly in front of their sibling.

Mar 10, 2023

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