Finding the Fourth Proportional to 92.20, 137.50 and 78.57

Step by Step Solution

1. Step 1: Write the proportion equation
   92.20 : 137.50 = 78.57 : x
2. Step 2: Convert to fraction form
   92.20/137.50 = 78.57/x
3. Step 3: Cross multiply
   92.20x = 137.50 × 78.57
4. Step 4: Simplify right side
   92.20x = 10,802.98
5. Step 5: Solve for x
   x = 10,802.98/92.20
6. Step 6: Final answer
   x = 117.18