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Finding the Fourth Proportional to 987.36, 1,478.56 and 661.72

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Solution

The fourth proportional to 987.36, 1,478.56 and 661.72 is: 990.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.36 : 1,478.56 = 661.72 : x
  2. Step 2: Convert to fraction form
    987.36/1,478.56 = 661.72/x
  3. Step 3: Cross multiply
    987.36x = 1,478.56 × 661.72
  4. Step 4: Simplify right side
    987.36x = 978,392.72
  5. Step 5: Solve for x
    x = 978,392.72/987.36
  6. Step 6: Final answer
    x = 990.92

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.