Finding the Fourth Proportional to 105.72, 145.90 and 59.10

Step by Step Solution

1. Step 1: Write the proportion equation
   105.72 : 145.90 = 59.10 : x
2. Step 2: Convert to fraction form
   105.72/145.90 = 59.10/x
3. Step 3: Cross multiply
   105.72x = 145.90 × 59.10
4. Step 4: Simplify right side
   105.72x = 8,622.69
5. Step 5: Solve for x
   x = 8,622.69/105.72
6. Step 6: Final answer
   x = 81.56