Home / 640.78-960.87-380.81

Finding the Fourth Proportional to 640.78, 960.87 and 380.81

Calculator

Solution

The fourth proportional to 640.78, 960.87 and 380.81 is: 571.04

Step by Step Solution

  1. Step 1: Write the proportion equation
    640.78 : 960.87 = 380.81 : x
  2. Step 2: Convert to fraction form
    640.78/960.87 = 380.81/x
  3. Step 3: Cross multiply
    640.78x = 960.87 × 380.81
  4. Step 4: Simplify right side
    640.78x = 365,912.39
  5. Step 5: Solve for x
    x = 365,912.39/640.78
  6. Step 6: Final answer
    x = 571.04

Related Problems

Find fourth proportional to 320.39, 480.43 and 190.41
Half scale
Find fourth proportional to 1,281.56, 1,921.74 and 761.63
Double scale
Find fourth proportional to 641.78, 962.37 and 381.81
Similar ratio
Find fourth proportional to 961.17, 1,441.30 and 571.22
1.5x scale

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.