Finding the Fourth Proportional to 100.31, 138.58 and 99.50

Step by Step Solution

1. Step 1: Write the proportion equation
   100.31 : 138.58 = 99.50 : x
2. Step 2: Convert to fraction form
   100.31/138.58 = 99.50/x
3. Step 3: Cross multiply
   100.31x = 138.58 × 99.50
4. Step 4: Simplify right side
   100.31x = 13,787.77
5. Step 5: Solve for x
   x = 13,787.77/100.31
6. Step 6: Final answer
   x = 137.46