Finding the Fourth Proportional to 20,964.72, 28,938.42 and 13,011.60

Step by Step Solution

1. Step 1: Write the proportion equation
   20,964.72 : 28,938.42 = 13,011.60 : x
2. Step 2: Convert to fraction form
   20,964.72/28,938.42 = 13,011.60/x
3. Step 3: Cross multiply
   20,964.72x = 28,938.42 × 13,011.60
4. Step 4: Simplify right side
   20,964.72x = 376,535,145.67
5. Step 5: Solve for x
   x = 376,535,145.67/20,964.72
6. Step 6: Final answer
   x = 17,960.42