Question

at what temperature will be the centigrade scaleand the farenheit will have some reading

Answer 1

At -40° the temperatures will be same.

Answer 2

$c = \frac{5}{9} (f - 32) \\ f = \frac{5}{9} (f - 32) \\ 9f = 5f - 160 \\ 4f = - 160 \\ f = - 40$
celcius and farenheit are equal to each other at -40
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