Don't Let Yourself Get Tricked!

Algebra Level 3

I'm sitting in a room at $20^{\circ}C$ when all of a sudden it warms to $40^{\circ}C$ .

What is the percent change, to the nearest integer, in the temperature $T$ ?

Details & Assumptions :

The formula for percent change between $x_{1}$ and $x_{2}$ is $\Delta$ % $= 100\large{\frac{x_{2}-x_{1}}{x_{1}}}$ .

None of These! 53% 19% 100% -24% 7% 0%

3 solutions

Alex Delhumeau
Jun 22, 2015

To find the percent change, we must first convert to Kelvins- a fixed scale. This is done by adding $273.15$ to the centigrade value.

$20^{\circ}C=293.15K \\ 40^{\circ}C=313.15K$

$\Delta$ % $=100\frac{313.15-293.15}{293.15}$ = $\frac{2000}{293.15}=6.82244...$ $\approx$ 7%

Isn't 0 degree celsius=273.15 K? So should'nt it be 273.15 is added to 20 and 40 respectively? And you have also written the converted temperatures as 293.15 K = 20+273.15 and 313.15 K = 40+273.15.

Debashruto Bhattacharyya - 5 years, 11 months ago

I'm having trouble understanding what you're saying, but as far as I understand my conversions are just fine.

Alex Delhumeau - 5 years, 11 months ago

You have a typo in the second sentence. Your calculations are correct. But in the second sentence, you said you add 275.15 to the centigrade value.

Matt Steele - 5 years, 11 months ago

@Matt Steele – yes, the calculations are correct--just change 275.15 to 273.15

Marvin Viray - 5 years, 11 months ago

@Matt Steele – Thanks. Fixed Now.

Alex Delhumeau - 5 years, 11 months ago

this is chitting that x2,,x1 must be in kelvin..?

Tarun Vaghela - 5 years, 11 months ago

Agastya Chandrakant
Jun 24, 2015

SI unit (Kelvin) that's the tricky part. Free points! Yay!

Mohit Gupta
Jun 23, 2015

Well its just a sort of tricky problem. Chanfe temp. To Kelvin

Don't Let Yourself Get Tricked!

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