Finding the Fourth Proportional to 1,086.60, 1,627.50 and 813

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.60 : 1,627.50 = 813 : x
2. Step 2: Convert to fraction form
   1,086.60/1,627.50 = 813/x
3. Step 3: Cross multiply
   1,086.60x = 1,627.50 × 813
4. Step 4: Simplify right side
   1,086.60x = 1,323,157.50
5. Step 5: Solve for x
   x = 1,323,157.50/1,086.60
6. Step 6: Final answer
   x = 1,217.70