Finding the Fourth Proportional to 100.42, 138.54 and 74.50

Step by Step Solution

1. Step 1: Write the proportion equation
   100.42 : 138.54 = 74.50 : x
2. Step 2: Convert to fraction form
   100.42/138.54 = 74.50/x
3. Step 3: Cross multiply
   100.42x = 138.54 × 74.50
4. Step 4: Simplify right side
   100.42x = 10,321.23
5. Step 5: Solve for x
   x = 10,321.23/100.42
6. Step 6: Final answer
   x = 102.78