Home / 642.78-957.38-639.68

Finding the Fourth Proportional to 642.78, 957.38 and 639.68

Calculator

Solution

The fourth proportional to 642.78, 957.38 and 639.68 is: 952.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    642.78 : 957.38 = 639.68 : x
  2. Step 2: Convert to fraction form
    642.78/957.38 = 639.68/x
  3. Step 3: Cross multiply
    642.78x = 957.38 × 639.68
  4. Step 4: Simplify right side
    642.78x = 612,408.85
  5. Step 5: Solve for x
    x = 612,408.85/642.78
  6. Step 6: Final answer
    x = 952.75

Related Problems

Find fourth proportional to 321.39, 478.69 and 319.84
Half scale
Find fourth proportional to 1,285.56, 1,914.75 and 1,279.35
Double scale
Find fourth proportional to 643.78, 958.86 and 640.68
Similar ratio
Find fourth proportional to 964.17, 1,436.06 and 959.51
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.