What’s the best and fastest way to do practise test 3, section 3, question 15? How would you interpret the equation? (which I find very confusing and difficult)

Thank you

If the equation is confusing for you, try plugging in! The three statements you’re evaluating are about 1 degree increases, so plug in 0 and 1 for F and see what happens to C. Then plug in 0 and 1 for C and see what happens to F.

C=\dfrac{5}{9}(0-32)\\\\C=\dfrac{-160}{9}

C=\dfrac{5}{9}(1-32)\\\\C=\dfrac{-155}{9}

That tells you that a 1 degree increase in F results in a \dfrac{5}{9} increase in C.

0=\dfrac{5}{9}(F-32)\\\\0=F-32\\\\32=F

1=\dfrac{5}{9}(F-32)\\\\\dfrac{9}{5}=F-32\\\\\dfrac{9}{5}+32=F

Because \dfrac{9}{5}=1.8, that tells you that a 1 degree increase in C results in a 1.8 degree increase in F.

That’s enough to choose choice D.

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