Finding the Fourth Proportional to 57,128.72, 78,837.64 and 31,978

Step by Step Solution

1. Step 1: Write the proportion equation
   57,128.72 : 78,837.64 = 31,978 : x
2. Step 2: Convert to fraction form
   57,128.72/78,837.64 = 31,978/x
3. Step 3: Cross multiply
   57,128.72x = 78,837.64 × 31,978
4. Step 4: Simplify right side
   57,128.72x = 2,521,070,051.92
5. Step 5: Solve for x
   x = 2,521,070,051.92/57,128.72
6. Step 6: Final answer
   x = 44,129.64