Finding the Fourth Proportional to 65,431.72, 90,293.50 and 39,980.69

Step by Step Solution

1. Step 1: Write the proportion equation
   65,431.72 : 90,293.50 = 39,980.69 : x
2. Step 2: Convert to fraction form
   65,431.72/90,293.50 = 39,980.69/x
3. Step 3: Cross multiply
   65,431.72x = 90,293.50 × 39,980.69
4. Step 4: Simplify right side
   65,431.72x = 3,609,996,432.52
5. Step 5: Solve for x
   x = 3,609,996,432.52/65,431.72
6. Step 6: Final answer
   x = 55,171.96