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Finding the Fourth Proportional to 1,187.15, 1,638.42 and 689.90

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Solution

The fourth proportional to 1,187.15, 1,638.42 and 689.90 is: 952.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.15 : 1,638.42 = 689.90 : x
  2. Step 2: Convert to fraction form
    1,187.15/1,638.42 = 689.90/x
  3. Step 3: Cross multiply
    1,187.15x = 1,638.42 × 689.90
  4. Step 4: Simplify right side
    1,187.15x = 1,130,345.96
  5. Step 5: Solve for x
    x = 1,130,345.96/1,187.15
  6. Step 6: Final answer
    x = 952.15

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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.