Finding the Fourth Proportional to 28,521.78, 42,782.76 and 12,921.18

Step by Step Solution

1. Step 1: Write the proportion equation
   28,521.78 : 42,782.76 = 12,921.18 : x
2. Step 2: Convert to fraction form
   28,521.78/42,782.76 = 12,921.18/x
3. Step 3: Cross multiply
   28,521.78x = 42,782.76 × 12,921.18
4. Step 4: Simplify right side
   28,521.78x = 552,803,742.86
5. Step 5: Solve for x
   x = 552,803,742.86/28,521.78
6. Step 6: Final answer
   x = 19,381.81