Finding the Fourth Proportional to 100.03, 138.15 and 72.40

Step by Step Solution

1. Step 1: Write the proportion equation
   100.03 : 138.15 = 72.40 : x
2. Step 2: Convert to fraction form
   100.03/138.15 = 72.40/x
3. Step 3: Cross multiply
   100.03x = 138.15 × 72.40
4. Step 4: Simplify right side
   100.03x = 10,002.06
5. Step 5: Solve for x
   x = 10,002.06/100.03
6. Step 6: Final answer
   x = 99.99