bingboy

avatar
Usernamebingboy
Score743
Membership
Stats
Questions 144
Answers 119

 #1
avatar+743 
0
Aug 18, 2024
 #1
avatar+743 
-1

Let's denote the number of workers initially hired as \( n = 5 \), and the total work required to complete the job as \( W \).

 

Let \( r \) be the work rate of one worker (i.e., the amount of work one worker can do in one day). Then the work rate of \( n \) workers is \( nr \), and the time it takes \( n \) workers to complete the job is:

 

\[
\text{Time} = \frac{W}{nr}
\]

 

### Step 1: Set up the equation for one additional worker


If one additional worker is hired, the total number of workers becomes \( n+1 \), and they can complete the job 12 days earlier. Therefore, the time it would take \( n+1 \) workers to complete the job is:

 

\[
\frac{W}{(n+1)r} = \frac{W}{nr} - 12
\]

 

We now substitute \( \frac{W}{nr} \) with the initial time \( T \):

 

\[
\frac{W}{(n+1)r} = T - 12
\]

 

Equating the two expressions for time:

 

\[
\frac{W}{(n+1)r} = \frac{W}{nr} - 12
\]

 

### Step 2: Solve for \( T \)


Substitute \( T = \frac{W}{nr} \):

 

\[
\frac{W}{(n+1)r} = \frac{W}{nr} - 12
\]

 

Multiply both sides by \( (n+1)r \) to clear the fractions:

 

\[
W = \frac{W(n+1)}{n} - 12(n+1)r
\]

 

Simplify and solve for \( T \):

 

\[
W = \frac{Wn + W}{n} - 12(n+1)r
\]

 

Simplify the equation:

 

\[
W = W + 12nr - 12r = 12nr \quad \Rightarrow \quad T = \frac{W}{nr} = 12
\]

 

Now, let's calculate the number of additional workers needed to complete the job 32 days earlier.

 

### Step 3: Set up the equation for \( k \) additional workers


If \( k \) additional workers are hired, the total number of workers becomes \( n + k \), and they can complete the job 32 days earlier. The equation for time is now:

 

\[
\frac{W}{(n+k)r} = T - 32
\]

 

Using the expression \( T = \frac{W}{nr} \):

 

\[
\frac{W}{(n+k)r} = \frac{W}{nr} - 32
\]

 

Multiply both sides by \( (n+k)r \):

 

\[
W = \frac{W(n+k)}{n} - 32(n+k)r
\]

 

Simplify the equation:

 

\[
W = W + 32(nr) - 32r = 32nr
\]

 

Now solve for \( k \):

 

\[
\frac{W}{nr} - \frac{W}{(n+k)r} = 32 \quad \Rightarrow \quad k = 8
\]

 

### Final Answer


Thus, 8 additional workers should be hired to complete the job 32 days earlier. The correct answer is:

\[
\boxed{8}
\]

Aug 10, 2024
 #2
avatar+743 
+2

Analyzing the Given Information:

 

Convex Pentagon: ABTCD is a convex pentagon, meaning all interior angles are less than 180 degrees.

 

Equal Sides: AB = CD implies sides AB and CD are congruent.

 

Internally Tangent Circles: The circumcircles of triangles TAB and TCD touch each other inside the pentagon.

 

Right Angle: Angle ATD is a right angle (90 degrees).

 

Angles and Sides: Angle BTC is 120 degrees, BT = 4 (length of side BT), and CT = 5 (length of side CT).

 

Key Points for Area Calculation:

 

Right Triangle: Triangle TAD is a right triangle due to angle ATD being 90 degrees.

 

Power of a Point: Since the circumcircles of TAB and TCD are internally tangent, point T is the power of point A with respect to circle BTC.

 

This means the product of TA and its projection onto BT (let's call it AP) is equal to the square of BT (which is 4).

 

Solving for AP and Area of Triangle TAD:

 

Projecting AP: Since triangle BTC is isosceles with angle BTC = 120 degrees, line BT bisects angle ABC. This means projection point P lies on line BT.

 

Using Power of a Point: Since T is the power of point A with respect to circle BTC, we have:

TA * AP = BT^2 (given)

 

Substitute known values: TA * AP = 4^2 = 16

 

Pythagorean Theorem in Triangle TAP: We know AP and need to find TA (the hypotenuse) and the area of triangle TAD (which is 1/2 * base * height).

 

Use the Pythagorean theorem: TA^2 = AP^2 + TP^2 (where TP is the leg opposite the right angle)

 

Substitute known values from step 2: TA^2 = 16 + TP^2

 

Finding TP: Since BT bisects angle ABC, triangle ABT is a 30-60-90 triangle with BT = 4 (half of the hypotenuse) and CT = 5 (the other leg). This implies AB = 2 * BT = 8 (hypotenuse).

 

Using Pythagoras in triangle ABT: TP^2 = AB^2 - BT^2 = 8^2 - 4^2 = 48

 

Finding TA and Area of Triangle TAD:

 

Substitute TP^2 from step 4 into the equation from step 3: TA^2 = 16 + 48 = 64

 

Take the square root of both sides to find TA: TA = 8

 

Now calculate the area of triangle TAD: Area = 1/2 * base * height = 1/2 * 4 (base TD) * 8 (height TA) = 16

 

Answer:

 

Therefore, the area of triangle TAD is 16.

Apr 9, 2024