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Finding the Fourth Proportional to 1,240, 1,711.20 and 688

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Solution

The fourth proportional to 1,240, 1,711.20 and 688 is: 949.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,240 : 1,711.20 = 688 : x
  2. Step 2: Convert to fraction form
    1,240/1,711.20 = 688/x
  3. Step 3: Cross multiply
    1,240x = 1,711.20 × 688
  4. Step 4: Simplify right side
    1,240x = 1,177,305.60
  5. Step 5: Solve for x
    x = 1,177,305.60/1,240
  6. Step 6: Final answer
    x = 949.44

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.