Finding the Fourth Proportional to 1,389.42, 1,918.02 and 917.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.42 : 1,918.02 = 917.60 : x
2. Step 2: Convert to fraction form
   1,389.42/1,918.02 = 917.60/x
3. Step 3: Cross multiply
   1,389.42x = 1,918.02 × 917.60
4. Step 4: Simplify right side
   1,389.42x = 1,759,965.56
5. Step 5: Solve for x
   x = 1,759,965.56/1,389.42
6. Step 6: Final answer
   x = 1,266.69