Finding the Fourth Proportional to 83.89, 126.46 and 78.31

Step by Step Solution

1. Step 1: Write the proportion equation
   83.89 : 126.46 = 78.31 : x
2. Step 2: Convert to fraction form
   83.89/126.46 = 78.31/x
3. Step 3: Cross multiply
   83.89x = 126.46 × 78.31
4. Step 4: Simplify right side
   83.89x = 9,902.69
5. Step 5: Solve for x
   x = 9,902.69/83.89
6. Step 6: Final answer
   x = 118.05