Finding the Fourth Proportional to 1,085.40, 1,498.30 and 643.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.40 : 1,498.30 = 643.34 : x
2. Step 2: Convert to fraction form
   1,085.40/1,498.30 = 643.34/x
3. Step 3: Cross multiply
   1,085.40x = 1,498.30 × 643.34
4. Step 4: Simplify right side
   1,085.40x = 963,918.46
5. Step 5: Solve for x
   x = 963,918.46/1,085.40
6. Step 6: Final answer
   x = 888.08