Finding the Fourth Proportional to 85.89, 128.72 and 61.79

Step by Step Solution

1. Step 1: Write the proportion equation
   85.89 : 128.72 = 61.79 : x
2. Step 2: Convert to fraction form
   85.89/128.72 = 61.79/x
3. Step 3: Cross multiply
   85.89x = 128.72 × 61.79
4. Step 4: Simplify right side
   85.89x = 7,953.61
5. Step 5: Solve for x
   x = 7,953.61/85.89
6. Step 6: Final answer
   x = 92.60