Finding the Fourth Proportional to 83.72, 115.49 and 78.59

Step by Step Solution

1. Step 1: Write the proportion equation
   83.72 : 115.49 = 78.59 : x
2. Step 2: Convert to fraction form
   83.72/115.49 = 78.59/x
3. Step 3: Cross multiply
   83.72x = 115.49 × 78.59
4. Step 4: Simplify right side
   83.72x = 9,076.84
5. Step 5: Solve for x
   x = 9,076.84/83.72
6. Step 6: Final answer
   x = 108.42