Finding the Fourth Proportional to 1,390.10, 1,918.74 and 918.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.10 : 1,918.74 = 918.34 : x
2. Step 2: Convert to fraction form
   1,390.10/1,918.74 = 918.34/x
3. Step 3: Cross multiply
   1,390.10x = 1,918.74 × 918.34
4. Step 4: Simplify right side
   1,390.10x = 1,762,055.69
5. Step 5: Solve for x
   x = 1,762,055.69/1,390.10
6. Step 6: Final answer
   x = 1,267.57