Without a calc. why does 9/5 equal 1.8 and not .555?

Question

I have to answer this question without using a calculator.

F=(9/5)(20)+32

 

wouldn't I write on the paper 9l5 not 5l9

Answer 1

The formula you wrote looks much like:

    F = (9/5)C + 32

 

[also note:  C = (F-32)(5/9) ]

 

If C=20, what is F (without using a calculator)?

  Well, since C is positive, F is at least 32.

   (1/5)(20) = 4 and 9*4 = 36, so 32+36 is 66°F.

 

Now, just for practice (and to check your answer):

    What is C when F=66  ???

Answer 2

9/5 = 1 4/5 

 

4/5 = 8/10 = 0.8

 

1 + 4/5 = 1 + 0.8 = 1.8

 

9/5 means 9 divided by 5, or how many times does 5 go into 9