Finding the Fourth Proportional to 1,317.89, 1,817.59 and 987.10

Step by Step Solution

1. Step 1: Write the proportion equation
   1,317.89 : 1,817.59 = 987.10 : x
2. Step 2: Convert to fraction form
   1,317.89/1,817.59 = 987.10/x
3. Step 3: Cross multiply
   1,317.89x = 1,817.59 × 987.10
4. Step 4: Simplify right side
   1,317.89x = 1,794,143.09
5. Step 5: Solve for x
   x = 1,794,143.09/1,317.89
6. Step 6: Final answer
   x = 1,361.38