Finding the Fourth Proportional to 42,780.30, 64,116.98 and 20,587.71

Step by Step Solution

1. Step 1: Write the proportion equation
   42,780.30 : 64,116.98 = 20,587.71 : x
2. Step 2: Convert to fraction form
   42,780.30/64,116.98 = 20,587.71/x
3. Step 3: Cross multiply
   42,780.30x = 64,116.98 × 20,587.71
4. Step 4: Simplify right side
   42,780.30x = 1,320,021,790.32
5. Step 5: Solve for x
   x = 1,320,021,790.32/42,780.30
6. Step 6: Final answer
   x = 30,855.83