Finding the Fourth Proportional to 78.78, 108.90 and 72.02

Step by Step Solution

1. Step 1: Write the proportion equation
   78.78 : 108.90 = 72.02 : x
2. Step 2: Convert to fraction form
   78.78/108.90 = 72.02/x
3. Step 3: Cross multiply
   78.78x = 108.90 × 72.02
4. Step 4: Simplify right side
   78.78x = 7,842.98
5. Step 5: Solve for x
   x = 7,842.98/78.78
6. Step 6: Final answer
   x = 99.56