10. The missing conversion is 20.32 inches
11. Total number of red cars is 34
12. Total number of blue cars is 36
13. Total number of silver cars is 70
<h3>What is Ratio?</h3>
Ratio is the number of times a quantity is contained more  or less than another in a whole.
Analysis:
10. If 1 inch = 2.54cm
      Then 8 inches = 8 x 2.54cm = 20.32 cm
      First car park: Total number of cars = 60
      ratio of red:blue:silver = 1:2:3
      Total ratio = 1+2+3 = 6
      number of red cars = 1/6 x 60 = 10
      number of blue cars = 2/6 x 60 = 20 cars
      number of silver cars = 3/6 x 60 = 30
    second car park: Total number of cars = 80
     ratio of blue: red: silver = 2:3:5
     total ratio = 2+3+5 = 10
     number of red cars = 3/10 x 80 = 24
     number of blue cars = 2/10 x 80 = 16
     number of silver cars = 5/10 x 80 = 40
11.  Total number of red cars = 10+24 = 34
12.  Total number of blue cars = 20+16 = 36
13.  Total number of silver cars = 30+40 = 70
Learn more about ratio: brainly.com/question/2328454
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