Finding the Fourth Proportional to 105.78, 145.98 and 59.15

Step by Step Solution

1. Step 1: Write the proportion equation
   105.78 : 145.98 = 59.15 : x
2. Step 2: Convert to fraction form
   105.78/145.98 = 59.15/x
3. Step 3: Cross multiply
   105.78x = 145.98 × 59.15
4. Step 4: Simplify right side
   105.78x = 8,635.08
5. Step 5: Solve for x
   x = 8,635.08/105.78
6. Step 6: Final answer
   x = 81.63