Finding the Fourth Proportional to 85.58, 128.18 and 61.16

Step by Step Solution

1. Step 1: Write the proportion equation
   85.58 : 128.18 = 61.16 : x
2. Step 2: Convert to fraction form
   85.58/128.18 = 61.16/x
3. Step 3: Cross multiply
   85.58x = 128.18 × 61.16
4. Step 4: Simplify right side
   85.58x = 7,839.49
5. Step 5: Solve for x
   x = 7,839.49/85.58
6. Step 6: Final answer
   x = 91.60