Finding the Fourth Proportional to 99.51, 137.29 and 78.72

Step by Step Solution

1. Step 1: Write the proportion equation
   99.51 : 137.29 = 78.72 : x
2. Step 2: Convert to fraction form
   99.51/137.29 = 78.72/x
3. Step 3: Cross multiply
   99.51x = 137.29 × 78.72
4. Step 4: Simplify right side
   99.51x = 10,807.47
5. Step 5: Solve for x
   x = 10,807.47/99.51
6. Step 6: Final answer
   x = 108.61