Finding the Fourth Proportional to 123.78, 185.70 and 78.42

Step by Step Solution

1. Step 1: Write the proportion equation
   123.78 : 185.70 = 78.42 : x
2. Step 2: Convert to fraction form
   123.78/185.70 = 78.42/x
3. Step 3: Cross multiply
   123.78x = 185.70 × 78.42
4. Step 4: Simplify right side
   123.78x = 14,562.59
5. Step 5: Solve for x
   x = 14,562.59/123.78
6. Step 6: Final answer
   x = 117.65