Finding the Fourth Proportional to 105.72, 145.91 and 61.47

Step by Step Solution

1. Step 1: Write the proportion equation
   105.72 : 145.91 = 61.47 : x
2. Step 2: Convert to fraction form
   105.72/145.91 = 61.47/x
3. Step 3: Cross multiply
   105.72x = 145.91 × 61.47
4. Step 4: Simplify right side
   105.72x = 8,969.09
5. Step 5: Solve for x
   x = 8,969.09/105.72
6. Step 6: Final answer
   x = 84.84