Finding the Fourth Proportional to 80,421.72, 120,509.57 and 42,987.12

Step by Step Solution

1. Step 1: Write the proportion equation
   80,421.72 : 120,509.57 = 42,987.12 : x
2. Step 2: Convert to fraction form
   80,421.72/120,509.57 = 42,987.12/x
3. Step 3: Cross multiply
   80,421.72x = 120,509.57 × 42,987.12
4. Step 4: Simplify right side
   80,421.72x = 5,180,359,131.80
5. Step 5: Solve for x
   x = 5,180,359,131.80/80,421.72
6. Step 6: Final answer
   x = 64,414.93