KJSEA 2025 Maths Q12 — Converting Kelvin to Degrees Celsius
Published
The Question
“The temperature of a liquid was recorded as minus 15 Kelvin. Which calculation gives the correct temperature in degrees Celsius? (The options are multiple-choice calculations, and the correct one is option D.)”
Recall the conversion rule
Kelvin and Celsius are two scales for measuring the same thing, temperature. They are separated by a fixed gap of 273 units, so you can always move from one scale to the other by adding or subtracting 273. To go from Kelvin down to Celsius, you subtract 273 from the Kelvin value.
Put in the given value
The recorded temperature is minus 15 Kelvin, so this is the number that takes the place of the Kelvin value in the rule. Substituting it in, the calculation becomes minus 15 take away 273. Notice that you keep the minus 15 exactly as given and simply subtract 273 from it.
Match to the correct option
Compare the calculation you built with the choices offered. The expression minus 15 minus 273 is the one written as option D, so that is the calculation that correctly converts the reading to degrees Celsius.
The question only asks which calculation is correct, so you identify the expression rather than work out its value.
Final Result
The correct calculation is minus 15 minus 273, which is option D.
Why this method works
The Celsius and Kelvin scales rise in step with each other, one degree at a time, but their zero points are set 273 units apart. Because of this fixed offset, converting a Kelvin reading to Celsius is always the single move of subtracting 273. Substituting the given reading of minus 15 into that rule gives minus 15 minus 273, so option D is the faithful translation of the rule into a calculation.
Working it out, minus 15 minus 273 equals minus 288 degrees Celsius, a single sensible temperature, confirming the calculation is set up correctly.