Finding the Fourth Proportional to 99.87, 137.63 and 78.00

Step by Step Solution

1. Step 1: Write the proportion equation
   99.87 : 137.63 = 78.00 : x
2. Step 2: Convert to fraction form
   99.87/137.63 = 78.00/x
3. Step 3: Cross multiply
   99.87x = 137.63 × 78.00
4. Step 4: Simplify right side
   99.87x = 10,734.82
5. Step 5: Solve for x
   x = 10,734.82/99.87
6. Step 6: Final answer
   x = 107.49