Finding the Fourth Proportional to 83.55, 124.49 and 78.31

Step by Step Solution

1. Step 1: Write the proportion equation
   83.55 : 124.49 = 78.31 : x
2. Step 2: Convert to fraction form
   83.55/124.49 = 78.31/x
3. Step 3: Cross multiply
   83.55x = 124.49 × 78.31
4. Step 4: Simplify right side
   83.55x = 9,748.51
5. Step 5: Solve for x
   x = 9,748.51/83.55
6. Step 6: Final answer
   x = 116.68