Finding the Fourth Proportional to 85.33, 128.13 and 78.58

Step by Step Solution

1. Step 1: Write the proportion equation
   85.33 : 128.13 = 78.58 : x
2. Step 2: Convert to fraction form
   85.33/128.13 = 78.58/x
3. Step 3: Cross multiply
   85.33x = 128.13 × 78.58
4. Step 4: Simplify right side
   85.33x = 10,068.46
5. Step 5: Solve for x
   x = 10,068.46/85.33
6. Step 6: Final answer
   x = 117.99