Finding the Fourth Proportional to 100.58, 138.72 and 71.42

Step by Step Solution

1. Step 1: Write the proportion equation
   100.58 : 138.72 = 71.42 : x
2. Step 2: Convert to fraction form
   100.58/138.72 = 71.42/x
3. Step 3: Cross multiply
   100.58x = 138.72 × 71.42
4. Step 4: Simplify right side
   100.58x = 9,907.38
5. Step 5: Solve for x
   x = 9,907.38/100.58
6. Step 6: Final answer
   x = 98.50