Finding the Fourth Proportional to 99.78, 137.76 and 72.24

Step by Step Solution

1. Step 1: Write the proportion equation
   99.78 : 137.76 = 72.24 : x
2. Step 2: Convert to fraction form
   99.78/137.76 = 72.24/x
3. Step 3: Cross multiply
   99.78x = 137.76 × 72.24
4. Step 4: Simplify right side
   99.78x = 9,951.78
5. Step 5: Solve for x
   x = 9,951.78/99.78
6. Step 6: Final answer
   x = 99.74