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Finding the Fourth Proportional to 991.42, 1,368.60 and 642.28

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Solution

The fourth proportional to 991.42, 1,368.60 and 642.28 is: 886.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.42 : 1,368.60 = 642.28 : x
  2. Step 2: Convert to fraction form
    991.42/1,368.60 = 642.28/x
  3. Step 3: Cross multiply
    991.42x = 1,368.60 × 642.28
  4. Step 4: Simplify right side
    991.42x = 879,024.41
  5. Step 5: Solve for x
    x = 879,024.41/991.42
  6. Step 6: Final answer
    x = 886.63

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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.