Finding the Fourth Proportional to 139.81, 209.73 and 42.31

Step by Step Solution

1. Step 1: Write the proportion equation
   139.81 : 209.73 = 42.31 : x
2. Step 2: Convert to fraction form
   139.81/209.73 = 42.31/x
3. Step 3: Cross multiply
   139.81x = 209.73 × 42.31
4. Step 4: Simplify right side
   139.81x = 8,873.50
5. Step 5: Solve for x
   x = 8,873.50/139.81
6. Step 6: Final answer
   x = 63.47