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Finding the Fourth Proportional to 1,188.48, 1,640 and 691.28

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Solution

The fourth proportional to 1,188.48, 1,640 and 691.28 is: 953.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,188.48 : 1,640 = 691.28 : x
  2. Step 2: Convert to fraction form
    1,188.48/1,640 = 691.28/x
  3. Step 3: Cross multiply
    1,188.48x = 1,640 × 691.28
  4. Step 4: Simplify right side
    1,188.48x = 1,133,699.20
  5. Step 5: Solve for x
    x = 1,133,699.20/1,188.48
  6. Step 6: Final answer
    x = 953.91

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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.