For example, 4°C is 04°C. Mirror image of '04' is '40'. So 4°C equals 40°F.
And when there's a 1 in front, as in 125°F, look at that as 100 + 25°F. Mirror of 25°F is 52°C. So 52°C equals 125°F.
(*) If you can't remember F = C × 9/5 + 32 or, perhaps, remember it but can't compute the arithmetic easily.
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