Finding the Fourth Proportional to 78.84, 117.50 and 78.20

Step by Step Solution

1. Step 1: Write the proportion equation
   78.84 : 117.50 = 78.20 : x
2. Step 2: Convert to fraction form
   78.84/117.50 = 78.20/x
3. Step 3: Cross multiply
   78.84x = 117.50 × 78.20
4. Step 4: Simplify right side
   78.84x = 9,187.52
5. Step 5: Solve for x
   x = 9,187.52/78.84
6. Step 6: Final answer
   x = 116.53