tmua.me Medium Set B Paper 2 · Question 19

Thirty temperatures have a mean of $18^\circ\mathrm C$ .

When the temperatures are entered into a computer, ten are entered using their numerical values in degrees Fahrenheit. The other twenty are entered using their numerical values in degrees Celsius. The computer treats all thirty entries as degrees Celsius and reports a mean of $30^\circ\mathrm C$ .

The numerical Fahrenheit and Celsius values, $F$ and $C$ , are related by

F=\frac95 C+32.

What is the mean, in degrees Celsius, of the ten temperatures entered incorrectly?

5

\dfrac{20}{9}

18

41

37

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tmua.me Medium Set B Paper 2 · Q19