Finding the Fourth Proportional to 99.76, 137.58 and 78.88

Step by Step Solution

1. Step 1: Write the proportion equation
   99.76 : 137.58 = 78.88 : x
2. Step 2: Convert to fraction form
   99.76/137.58 = 78.88/x
3. Step 3: Cross multiply
   99.76x = 137.58 × 78.88
4. Step 4: Simplify right side
   99.76x = 10,852.31
5. Step 5: Solve for x
   x = 10,852.31/99.76
6. Step 6: Final answer
   x = 108.78