Home / 690.40-1,035.60-620.80

Finding the Fourth Proportional to 690.40, 1,035.60 and 620.80

Calculator

Solution

The fourth proportional to 690.40, 1,035.60 and 620.80 is: 931.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    690.40 : 1,035.60 = 620.80 : x
  2. Step 2: Convert to fraction form
    690.40/1,035.60 = 620.80/x
  3. Step 3: Cross multiply
    690.40x = 1,035.60 × 620.80
  4. Step 4: Simplify right side
    690.40x = 642,900.48
  5. Step 5: Solve for x
    x = 642,900.48/690.40
  6. Step 6: Final answer
    x = 931.20

Related Problems

Find fourth proportional to 345.20, 517.80 and 310.40
Half scale
Find fourth proportional to 1,380.80, 2,071.20 and 1,241.60
Double scale
Find fourth proportional to 691.40, 1,037.10 and 621.80
Similar ratio
Find fourth proportional to 1,035.60, 1,553.40 and 931.20
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.