Finding the Fourth Proportional to 1,390.69, 1,918.52 and 917.98

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.69 : 1,918.52 = 917.98 : x
2. Step 2: Convert to fraction form
   1,390.69/1,918.52 = 917.98/x
3. Step 3: Cross multiply
   1,390.69x = 1,918.52 × 917.98
4. Step 4: Simplify right side
   1,390.69x = 1,761,162.99
5. Step 5: Solve for x
   x = 1,761,162.99/1,390.69
6. Step 6: Final answer
   x = 1,266.40