Finding the Fourth Proportional to 1,085.91, 1,497.88 and 643.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.91 : 1,497.88 = 643.50 : x
2. Step 2: Convert to fraction form
   1,085.91/1,497.88 = 643.50/x
3. Step 3: Cross multiply
   1,085.91x = 1,497.88 × 643.50
4. Step 4: Simplify right side
   1,085.91x = 963,886.58
5. Step 5: Solve for x
   x = 963,886.58/1,085.91
6. Step 6: Final answer
   x = 887.63