Finding the Third Proportional to 87,491.50 and 128,139

Step by Step Solution

1. Step 1: Write the proportion equation
   87,491.50 : 128,139 = 128,139 : x
2. Step 2: Convert to fraction form
   87,491.50/128,139 = 128,139/x
3. Step 3: Cross multiply
   87,491.50x = 128,139 × 128,139
4. Step 4: Simplify right side
   87,491.50x = 16,419,603,321
5. Step 5: Solve for x
   x = 16,419,603,321/87,491.50
6. Step 6: Final answer
   x = 187,670.84