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Problem: Let a_1, a_2, a_3 be real numbers such that

|a_1 - a_2| + |a_2 - a_3| + |a_3 - a_1| = 100.
What is the largest possible value of |a_1 - a_2|?

Answer: 10

Here's how to find the radius of the circle:

Area of a Single White Sector:

We are given that the area of one white sector is 13π/54 square inches.

Proportion of White Sectors:

Since there are 21 sectors total and 3 are white, the white sectors represent 3/21 of the entire circle's area.

Full Circle Area:

To find the total area of the circle, we can divide the area of one white sector by its proportion (3/21) of the whole circle:

Total circle area = (Area of one white sector) / (Proportion of white sectors)

Total circle area = (13π/54 in²) / (3/21)

Circle Area Formula:

We know the area of a circle is calculated by πr², where r is the radius.

Equating Areas:

Since the total area we found represents the entire circle, we can equate it to the circle area formula:

πr² = (13π/54 in²) / (3/21)

Simplifying and Solving:

Cancel out common factors of π and simplify:

r² = (13 / 54) * (21 / 3) in²

r² = 13 in²

Take the square root of both sides (remembering that squaring can introduce extraneous solutions, so we'll check for those later).

r = √13 in ≈ 3.61 in (rounded to nearest hundredth)

Here's how to estimate the lifetime of the sun based on the given information:

Energy from Hydrogen Fusion:

Every time two hydrogen atoms fuse, they release 2.3 × 10^-13 J of energy.

Mass of Converted Hydrogen:

To find the total mass of hydrogen converted per second to generate the sun's power output, we can divide the power (energy per second) by the energy released per fusion:

Mass of converted hydrogen per second (m_h_converted) = Sun's power / Energy per fusion

m_h_converted = (3.6 × 10^26 J/s) / (2.3 × 10^-13 J/fusion)

m_h_converted ≈ 1.57 × 10^39 kg/s (This is the mass of hydrogen converted to helium every second)

Mass of Fused Hydrogen Over Time:

We are estimating the lifetime (t) of the sun. To find the total mass of hydrogen converted over that time, we multiply the mass converted per second by the lifetime:

Total mass of converted hydrogen (M_h_converted) = m_h_converted * t

Relating Converted Hydrogen to Initial Mass:

We know the initial mass of the sun (m_sun) is 2 × 10^30 kg. Since we assumed the sun started as pure hydrogen, this initial mass represents the total amount of hydrogen available for fusion.

Not all the mass of the hydrogen atom is converted to energy during fusion. A small amount is converted to helium, which has a slightly higher mass.

To account for this, we can introduce a factor (f) representing the fraction of the hydrogen mass that gets converted to energy. This factor is less than 1 (around 0.007).

M_h_converted = f * m_sun

Solving for Lifetime:

Now we can equate the total mass of converted hydrogen over time (from step 3) to the initial mass of the sun (adjusted for conversion efficiency) from step 4:

m_h_converted * t = f * m_sun

(1.57 × 10^39 kg/s) * t = f * (2 × 10^30 kg)

t = (f * 2 × 10^30 kg) / (1.57 × 10^39 kg/s)

Finding the Lifetime:

f = 0.01 (1% conversion):

Converting Seconds to Years:

There are 31,536,000 seconds in a year. Converting the estimated lifetimes:

For f = 0.01: Lifetime ≈ 1.27 × 10^11 seconds / (31,536,000 seconds/year) ≈ 4.03 × 10^3 years (around 4,000 years)

Absolutely, based on the formula and the constants provided, we can calculate the value of Planck's constant (h) from the experimental data.

Here's how:

Identify the Given Values:

f_peak (peak frequency): This value likely comes from your experiment and needs to be plugged in. We'll denote it as an unknown for now.

k_B (Boltzmann's constant): k_B ≈ 1.38 × 10^-23 m² kg s⁻² K⁻¹ (given)

T (temperature): This value likely comes from your experiment and needs to be plugged in. We'll denote it as an unknown for now.

Rearrange the Formula for h:

We want to isolate h on one side of the equation. The formula is:

f_peak = 2.821 * (k_B * T) / h

To solve for h, multiply both sides by h and divide both sides by 2.821 * k_B * T:

h = (f_peak * 2.821 * k_B * T) / (f_peak)

We can simplify this further since f_peak appears in both the numerator and denominator and cancels out:

h = 2.821 * k_B * T

Plug in Experimental Data:

Now, replace f_peak and T with the actual values you obtained from your experiment. Make sure the units are consistent.

h = 2.821 * (1.38 × 10^-23 m² kg s⁻² K⁻¹) * T (in Kelvin)

Note: Since k_B is a very small number, the final value of h will depend significantly on the measured values of f_peak and T.

Example:

Let's say your experiment measured a peak frequency of f_peak = 5.00 x 10^14 Hz (hertz) and the temperature of the black body was T = 6000 Kelvin.

h = 2.821 * (1.38 × 10^-23 m² kg s⁻² K⁻¹) * 6000 K

h ≈ 6.61 x 10^-34 J s (joules per second)

This is a typical range for the value of Planck's constant.

The largest possible value of D is 39.

The sum of the terms 1/(sqrt(a_1) + sqrt(a_2)) + ... is equal to 45.

The values of x that work are 1 and 3, so the answer is 1 + 3 = 4.

Problem 3

Imagine we make one such cut through a corner of the cube. Let s be the length of the cut, as shown below.

Since all the edges have the same length, the four triangles meeting at the point of the pyramid must all be equilateral.

Thus the sides of the square at the base of the pyramid all have length s. By the Pythagorean Theorem, s2+s2=62, so s=62​/2=32​.

The volume of each small pyramid is then 31​(32​)2⋅32​=9, so the volume removed from the cube is 8⋅9=72.

The volume of the original cube is 63=216, so the volume of the resulting polyhedron is 216 − 72 = 144​.

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To find all values of \( x \) for which \( f(x) > g(x) \), where \( f(x) = |x| \) and \( g(x) = x^2 \), we need to compare their values for different ranges of \( x \).

1. For \( x \geq 0 \):

\[ f(x) = |x| = x \]

\[ g(x) = x^2 \]

So, \( f(x) > g(x) \) for \( x \geq 0 \) when \( x^2 > x \), which is true when \( x > 1 \) or \( x < 0 \).

2. For \( x < 0 \):

\[ f(x) = |x| = -x \]

\[ g(x) = x^2 \]

So, \( f(x) > g(x) \) for \( x < 0 \) when \( -x > x^2 \), which is true when \( -x > x^2 \) for \( x < 0 \).

Let's solve \( -x > x^2 \) for \( x < 0 \):

\[ -x > x^2 \]

\[ x^2 + x < 0 \]

\[ x(x + 1) < 0 \]

This inequality holds true when either \( x < 0 \) and \( x + 1 > 0 \), or \( x > 0 \) and \( x + 1 < 0 \).

1. For \( x < 0 \), \( x(x + 1) < 0 \) when \( x < 0 \) and \( x + 1 > 0 \) (the product of two negative numbers is positive):

\[ x < 0 \]

\[ x + 1 > 0 \]

\[ x > -1 \]

So, for \( x < 0 \), \( f(x) > g(x) \) when \( -1 < x < 0 \).

Combining both ranges of \( x \), we have \( f(x) > g(x) \) for \( x > 1 \) or \( -1 < x < 0 \).

Therefore, all values of \( x \) for which \( f(x) > g(x) \) are \( x \in (-1, 0) \cup (1, \infty) \).

Let the distance driven be d miles.

We know time = distance/rate.

Traveling at 40 mph:

Time taken (t1) = d / 40 hours

Traveling at 15 mph:

Time taken (t2) = d / 15 hours

We are given that t2 - t1 = 45 minutes (convert to hours: 45 minutes = 45/60 hours = 3/4 hours)

Setting up the equation based on the given information: d / 15 - d / 40 = 3/4

Simplifying the equation: 4d - d = 120 (common denominator of 60) 3d = 120 d = 40 miles

Therefore, you drove for 40 miles to reach the beach.