Finding the Fourth Proportional to 139.88, 210.56 and 99.58

Step by Step Solution

1. Step 1: Write the proportion equation
   139.88 : 210.56 = 99.58 : x
2. Step 2: Convert to fraction form
   139.88/210.56 = 99.58/x
3. Step 3: Cross multiply
   139.88x = 210.56 × 99.58
4. Step 4: Simplify right side
   139.88x = 20,967.69
5. Step 5: Solve for x
   x = 20,967.69/139.88
6. Step 6: Final answer
   x = 149.90