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 #1
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Analyzing the Problem

 

Understanding the Geometry:

 

We have two concentric circles (circles with the same center).

 

A chord of the larger circle is tangent to the smaller circle. This means the chord is perpendicular to the radius of the smaller circle at the point of tangency.

 

We need to find the area of the ring-shaped region, which is the difference in areas between the larger and smaller circles.

 

Key Points:

 

The chord of the larger circle is the diameter of the smaller circle.

 

The radius of the smaller circle is half the length of the chord.

 

Solution

 

Find the radius of the smaller circle:

 

Since the chord is the diameter, the radius of the smaller circle is 10/2 = 5 units.

 

Find the area of the smaller circle:

 

Area of a circle = πr², where r is the radius.

 

Area of the smaller circle = π(5)² = 25π square units.

 

Find the radius of the larger circle:

 

The radius of the larger circle is the sum of the radius of the smaller circle and the distance from the center to the chord (which is the same as the radius of the smaller circle).

 

Radius of the larger circle = 5 + 5 = 10 units.

 

Find the area of the larger circle:

 

Area of the larger circle = π(10)² = 100π square units.

 

Find the area of the ring-shaped region:

 

Area of the ring-shaped region = Area of the larger circle - Area of the smaller circle.

 

Area of the ring-shaped region = 100π - 25π = 75π square units.

 

Therefore, the area of the ring-shaped region is 75π square units.

10.09.2024
 #2
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-1

The probability of drawing unmatched socks on any given day depends on the number of socks remaining and the number of matching pairs left. Let's analyze this step-by-step:

 

Day 1:

 

Total socks: 6 (2 red, 2 white, 2 blue)

 

Favorable outcomes (unmatched socks): You can draw any one sock and then a sock from a different pair. There are 4 choices for the first sock (any of the 6 colors) and then 4 remaining socks (excluding the one already drawn). So, there are 4 * 4 = 16 favorable outcomes.

 

Total possible outcomes: You can draw any two socks from the 6 available. There are 6 choices for the first sock and then 5 remaining socks, resulting in 6 * 5 = 30 total possible outcomes.

 

Probability on Day 1:

 

(Favorable outcomes on Day 1) / (Total possible outcomes on Day 1) = 16 / 30 = 8/15

 

Day 2:

 

Total socks remaining: 4 (after drawing 2 on Day 1, not replaced)

 

Favorable outcomes (unmatched socks): Similar to Day 1, you can draw any sock and then one from a different remaining pair. There are 3 choices for the first sock and then 2 remaining socks (excluding the one drawn), resulting in 3 * 2 = 6 favorable outcomes.

 

Total possible outcomes: There are 4 choices for the first sock and then 3 remaining, resulting in 4 * 3 = 12 total possible outcomes.

 

Probability on Day 2 (given unmatched socks on Day 1):

 

We only consider the scenario where you drew unmatched socks on Day 1 because the prompt asks for the probability of this happening for all three days.

 

So, we only consider the drawers where we have 4 socks remaining (unmatched).

 

(Favorable outcomes on Day 2) / (Total possible outcomes on Day 2) = 6 / 12 = 1/2

 

Day 3:

 

Total socks remaining: 2 (after drawing 2 on Day 2, not replaced)

 

Favorable outcomes (unmatched socks): There's only one way to draw unmatched socks at this point - you must draw the two remaining socks, which are inherently unmatched.

 

Total possible outcomes: There are 2 choices for the first sock and then 1 remaining, resulting in 2 * 1 = 2 total possible outcomes.

 

Probability on Day 3 (given unmatched socks on Days 1 & 2):

 

Similar to Day 2, we only consider the scenario where you drew unmatched socks on both previous days.

 

(Favorable outcomes on Day 3) / (Total possible outcomes on Day 3) = 1 / 2

 

Overall Probability:

 

The prompt asks for the probability of getting unmatched socks for all three days. To get this probability, we need to multiply the probabilities of getting unmatched socks on each day (considering the condition that you drew unmatched socks on the previous day).

 

Overall Probability = (Probability on Day 1) * (Probability on Day 2 | Day 1) * (Probability on Day 3 | Day 1 & 2) = 8/15 * 1/2 * 1/2 = 8 / 60

 

Simplifying the fraction:

 

We can divide both the numerator and denominator by 4:

 

Overall Probability = 2 / 15

 

Therefore, the probability of drawing unmatched socks for all three days is 2/15.

19.06.2024
 #1
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0

Analyzing f(x)⋅g(x)

 

We are asked to find several properties of the product of two polynomials, $f(x) = -x^2+ 8x - 5$ and $g(x) = x^3 - 11x^2 + 2x$.

 

Finding the Product:

 

The product f(x)⋅g(x) can be found using the distributive property or polynomial multiplication techniques. Here, we'll use the distributive property:

f(x) * g(x) = (-x^2 + 8x - 5) * (x^3 - 11x^2 + 2x)

 

Multiplying each term of f(x) by each term of g(x) and combining like terms will result in a fourth-degree polynomial.

 

Properties of the Product:

 

Leading Term:

 

The leading term in a polynomial is the term with the highest degree. In the product, the highest degree term will come from multiplying the highest degree terms of f(x) and g(x). These terms are -x^2 and x^3, respectively. Their product is -x^5. Therefore, the leading term of f(x) * g(x) is -x^5.

 

Leading Coefficient:

 

The leading coefficient is the coefficient of the leading term. In this case, the leading term is -x^5, and its coefficient is -1. Therefore, the leading coefficient is -1.

 

Degree:

 

The degree of a polynomial is the highest exponent of the variable. Since the leading term has a degree of 5, the degree of f(x) * g(x) is 5.

 

Constant Term:

 

The constant term is the term that doesn't include any variable (x). To find it, we identify the terms in the product that don't have any x. Multiplying the constant term of f(x) (-5) by the constant term of g(x) (2) will result in the constant term of the product. Additionally, there might be other terms that don't have x due to the product of other terms. After multiplying and combining like terms, you'll find the constant term.

 

Coefficient of x^2:

 

The coefficient of x^2 is the number multiplying the term with x^2. This can be found by identifying terms in the product that have x^2. Multiply terms in f(x) that contain x by terms in g(x) that contain x^2, and vice versa. Combine like terms to find the coefficient of x^2.

 

Finding these properties requires multiplying f(x) and g(x) and performing some term manipulation. However, the steps outlined above should guide you in finding each property.

19.06.2024
 #1
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0
19.06.2024
 #1
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0

Here's how to find the number of times the digit 9 appears in the list of all integers from 1 to 750:

Approach 1: Separating by Hundreds Place

We can break down the count into three sections based on the hundreds digit:

Numbers from 1 to 99:

Every unit digit (from 0 to 9) will appear 10 times (once in each number from 10 to 19, 20 to 29, and so on).

Since 9 is a unit digit, it appears 10 times in this range.

Numbers from 100 to 199:

The hundreds digit is always 1, so we only need to consider the tens and units digits.

Following the same logic as before, each digit (including 9) will appear 10 times in the tens place.

Therefore, 9 appears 10 times in this range.

Numbers from 200 to 750:

We again need to consider both the hundreds and tens/units digits.

The hundreds digit can be 2, 3, ..., 7 (6 different values).

For each hundreds digit value, the tens and units digits will each allow the digit 9 to appear 10 times (as explained earlier).

Counting the Occurrences:

Occurrences in 1-99: 10 times

Occurrences in 100-199: 10 times

Occurrences in 200-750: 6 hundreds digits * 10 occurrences/hundreds digit = 60 times

Total Occurrences:

Adding the occurrences from each section:

Total = 10 (from 1-99) + 10 (from 100-199) + 60 (from 200-750) = 80 times

Approach 2: Utilizing Digit Patterns

Another approach is to analyze the digit patterns within the range.

Single-digit numbers (1-9): The digit 9 appears once.

Two-digit numbers ending in 9 (from 19 to 99): Each number contributes the digit 9 once. There are 10 such numbers (9 total for 10s digit and 1 for the unit digit of 99).

Three-digit numbers with 9 in the tens or units place (from 109 to 759, and from 190 to 799): Similar to two-digit numbers, each number contributes the digit 9 once. There are 10 numbers for each placement of 9 (tens or units), resulting in 20 numbers.

Three-digit numbers with 9 in the hundreds place (from 900 to 999): Each number contributes the digit 9 twice. There are 100 such numbers (10 numbers from 900 to 909 and another 90 numbers from 910 to 999).

Counting the Occurrences:

Single digit: 1 time

Two-digit ending in 9: 10 times

Three-digit with 9 in tens/units: 20 times

Three-digit with 9 in hundreds: 100 times (each digit counted twice)

Total Occurrences:

Adding the occurrences from each pattern:

Total = 1 + 10 + 20 + 2 * 100 = 131 times

Addressing the Discrepancy:

The second approach seems to give a higher count (131) compared to the first approach (80). However, there's a double-counting error in the second approach.

Numbers like 199 and 909 are counted twice (once for 9 in tens place and again for 9 in units place).

Correcting the Count:

We need to subtract the number of times a three-digit number is counted twice for both tens and units digits containing 9.

There are 20 such numbers (as counted earlier).

Final Count:

Total occurrences (corrected) = 131 (initial count) - 20 (double-counted) = 111 times

This corrected count (111) is incorrect. The first approach (80) provides the accurate answer.

The mistake in the second approach highlights the importance of careful analysis and avoiding double-counting when dealing with digit patterns.

30.03.2024