Finding the Fourth Proportional to 1,008.72, 1,513.05 and 278.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,008.72 : 1,513.05 = 278.34 : x
2. Step 2: Convert to fraction form
   1,008.72/1,513.05 = 278.34/x
3. Step 3: Cross multiply
   1,008.72x = 1,513.05 × 278.34
4. Step 4: Simplify right side
   1,008.72x = 421,142.34
5. Step 5: Solve for x
   x = 421,142.34/1,008.72
6. Step 6: Final answer
   x = 417.50