Finding the Fourth Proportional to 83.12, 123.86 and 78.73

Step by Step Solution

1. Step 1: Write the proportion equation
   83.12 : 123.86 = 78.73 : x
2. Step 2: Convert to fraction form
   83.12/123.86 = 78.73/x
3. Step 3: Cross multiply
   83.12x = 123.86 × 78.73
4. Step 4: Simplify right side
   83.12x = 9,751.38
5. Step 5: Solve for x
   x = 9,751.38/83.12
6. Step 6: Final answer
   x = 117.32