Question

What is 89 Fahrenheit in Celsius?

Answer 1

`32^@"C"`

Explanation:

Celcius to Farenheit conversion

`(C-0)/(100-0)=(F-32)/(212-32)`

`C/100=(89-32)/180`

`C=57/180*100=57/9*5=95/3 ~= 32^@"C"`

Answer 2

`T_C=31.666...` degree Celsius.

Explanation:

This should be in the Physics section but anyway...

For this, you need to know the formula that converts Fahrenheit to Celsius.

Googling it, you will easily find that:
`T_C=(T_F - 32)*frac(5)(9)`

where `T_C` is the temperature in Celsius,
and `T_F` is the temperature in Fahrenheit.

So, since `T_F=89`, we have:

`T_C = (89-32)*frac(5)(9)`
so
`T_C = 57*frac(5)(9)`

I'm sure most people would pull out their calculator at this stage, but we could simplify it a bit more, if one notices that `57 = 30 +27 = 3*10+3*9=3*19`.
Then we can simplify the 3 (because `9=3*3`) and we have:
`T_C = 19*frac(5)(3)`

Then `19*5=95`, and we are left with:
`T_C = frac(95)(3)`

You could bust out your calculator at this point but we could go a bit further, if one notices that `95=93+2` where 93 is a multiple of 3.
`T_C=frac(93)(3)+frac(2)(3)`

Since `frac(93)(3)=31` and you do know that `frac(2)(3)=0.6666...` (well, you must know that `frac(1)(3)=0.33333...` so that `frac(2)(3)=0.66666...`),
we have:

`T_C=31.666...` degree Celsius.