Finding the Fourth Proportional to 120,638.72, 166,488 and 78,233.60

Step by Step Solution

1. Step 1: Write the proportion equation
   120,638.72 : 166,488 = 78,233.60 : x
2. Step 2: Convert to fraction form
   120,638.72/166,488 = 78,233.60/x
3. Step 3: Cross multiply
   120,638.72x = 166,488 × 78,233.60
4. Step 4: Simplify right side
   120,638.72x = 13,024,955,596.80
5. Step 5: Solve for x
   x = 13,024,955,596.80/120,638.72
6. Step 6: Final answer
   x = 107,966.63