Finding the Fourth Proportional to 31,138.12, 42,970.86 and 16,991.20

Step by Step Solution

1. Step 1: Write the proportion equation
   31,138.12 : 42,970.86 = 16,991.20 : x
2. Step 2: Convert to fraction form
   31,138.12/42,970.86 = 16,991.20/x
3. Step 3: Cross multiply
   31,138.12x = 42,970.86 × 16,991.20
4. Step 4: Simplify right side
   31,138.12x = 730,126,476.43
5. Step 5: Solve for x
   x = 730,126,476.43/31,138.12
6. Step 6: Final answer
   x = 23,447.99