Finding the Fourth Proportional to 99.72, 137.42 and 86.58

Step by Step Solution

1. Step 1: Write the proportion equation
   99.72 : 137.42 = 86.58 : x
2. Step 2: Convert to fraction form
   99.72/137.42 = 86.58/x
3. Step 3: Cross multiply
   99.72x = 137.42 × 86.58
4. Step 4: Simplify right side
   99.72x = 11,897.82
5. Step 5: Solve for x
   x = 11,897.82/99.72
6. Step 6: Final answer
   x = 119.31