Home / 720.15-990.14-640.70

Finding the Fourth Proportional to 720.15, 990.14 and 640.70

Calculator

Solution

The fourth proportional to 720.15, 990.14 and 640.70 is: 880.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    720.15 : 990.14 = 640.70 : x
  2. Step 2: Convert to fraction form
    720.15/990.14 = 640.70/x
  3. Step 3: Cross multiply
    720.15x = 990.14 × 640.70
  4. Step 4: Simplify right side
    720.15x = 634,382.70
  5. Step 5: Solve for x
    x = 634,382.70/720.15
  6. Step 6: Final answer
    x = 880.90

Related Problems

Find fourth proportional to 360.08, 495.07 and 320.35
Half scale
Find fourth proportional to 1,440.30, 1,980.28 and 1,281.40
Double scale
Find fourth proportional to 721.15, 991.51 and 641.70
Similar ratio
Find fourth proportional to 1,080.23, 1,485.21 and 961.05
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.