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Finding the Fourth Proportional to 1,221.78, 1,681.20 and 1,128.84

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Solution

The fourth proportional to 1,221.78, 1,681.20 and 1,128.84 is: 1,553.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.78 : 1,681.20 = 1,128.84 : x
  2. Step 2: Convert to fraction form
    1,221.78/1,681.20 = 1,128.84/x
  3. Step 3: Cross multiply
    1,221.78x = 1,681.20 × 1,128.84
  4. Step 4: Simplify right side
    1,221.78x = 1,897,805.81
  5. Step 5: Solve for x
    x = 1,897,805.81/1,221.78
  6. Step 6: Final answer
    x = 1,553.31

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1.5x scale

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.