Finding the Fourth Proportional to 1,987.84, 2,979.78 and 688.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,987.84 : 2,979.78 = 688.42 : x
2. Step 2: Convert to fraction form
   1,987.84/2,979.78 = 688.42/x
3. Step 3: Cross multiply
   1,987.84x = 2,979.78 × 688.42
4. Step 4: Simplify right side
   1,987.84x = 2,051,340.15
5. Step 5: Solve for x
   x = 2,051,340.15/1,987.84
6. Step 6: Final answer
   x = 1,031.94