Finding the Fourth Proportional to 105.98, 146.21 and 85.31

Step by Step Solution

1. Step 1: Write the proportion equation
   105.98 : 146.21 = 85.31 : x
2. Step 2: Convert to fraction form
   105.98/146.21 = 85.31/x
3. Step 3: Cross multiply
   105.98x = 146.21 × 85.31
4. Step 4: Simplify right side
   105.98x = 12,472.02
5. Step 5: Solve for x
   x = 12,472.02/105.98
6. Step 6: Final answer
   x = 117.69