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Finding the Fourth Proportional to 991.76, 1,368.36 and 642.80

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Solution

The fourth proportional to 991.76, 1,368.36 and 642.80 is: 886.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.76 : 1,368.36 = 642.80 : x
  2. Step 2: Convert to fraction form
    991.76/1,368.36 = 642.80/x
  3. Step 3: Cross multiply
    991.76x = 1,368.36 × 642.80
  4. Step 4: Simplify right side
    991.76x = 879,581.81
  5. Step 5: Solve for x
    x = 879,581.81/991.76
  6. Step 6: Final answer
    x = 886.89

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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.