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Finding the Fourth Proportional to 991.34, 1,493.70 and 821.78

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Solution

The fourth proportional to 991.34, 1,493.70 and 821.78 is: 1,238.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.34 : 1,493.70 = 821.78 : x
  2. Step 2: Convert to fraction form
    991.34/1,493.70 = 821.78/x
  3. Step 3: Cross multiply
    991.34x = 1,493.70 × 821.78
  4. Step 4: Simplify right side
    991.34x = 1,227,492.79
  5. Step 5: Solve for x
    x = 1,227,492.79/991.34
  6. Step 6: Final answer
    x = 1,238.22

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.