Question

the temperature of a liquid is 20 degrees celsius the liquid is cooled at the rate of 3 degree Celsius per hour.

i) What will be its temperature after 4 hours?
ii) After how long will it be -1 degree Celsius? ​

Answer 1

$\large\mathfrak\red{question}$

The temperature of a liquid is 20 degrees celsius the liquid is cooled at the rate of 3 degree Celsius per hour

$\large\mathfrak\green{to \: \: \: \: \: find}$

• What will be its temperature after 4 hours?

• After how long will it be -1 degree Celsius?

$\large\mathfrak\blue{Solution}$

at present,

temperature = 20°C

rate of decreasing per

hour = 3 °C

1. after 4 hours = 20 - (4× 3)

= 20 - 12

= 8°C

2. to attain -1°C

take the hours as 'n'

$\implies \: \: 20 - (3 \times n) = - 1$

$\implies \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:- 3n \: \: \:= - 21 \: \: \: \:$

$\implies \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: n \: = \frac{ - 21}{ - 3}$

$\implies \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: n \: \: = 7$

ie, after 7 hours , the temperature wil be -1°C