Finding the Fourth Proportional to 399.72, 599.59 and 139.72

Step by Step Solution

1. Step 1: Write the proportion equation
   399.72 : 599.59 = 139.72 : x
2. Step 2: Convert to fraction form
   399.72/599.59 = 139.72/x
3. Step 3: Cross multiply
   399.72x = 599.59 × 139.72
4. Step 4: Simplify right side
   399.72x = 83,774.02
5. Step 5: Solve for x
   x = 83,774.02/399.72
6. Step 6: Final answer
   x = 209.58