Question

The temperature of a room at 9 am was 20°C above zero. It increases at the rate of 2°C per hour until 12 noon, then it decreases at the rate of 3°C per hour until midnight. What would be the temperature at midnight

Answer 1

Answer:

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Solution :-

At 12 noon, the temperature = 10° C above zero

The temperature is decreasing at 2° C per hour

8° C below zero = - 8° C

So, total fall in temperature from 10° C to 0° C and from 0° C to - 8° C = 18° C

Since the temperature falls 2° C in every one hour.

Therefore, to decrease 18° C, time taken = 18/2

= 9 hours

Present time is 12 noon so, the time when the temperature is - 8° C

= 12 noon + 9 hours

So, The time at which the temperature will be - 8° C = 9 PM

At 9 PM, the temperature is - 8° C, the temperature at 12 midnight will be = 

(- 8° C) + (- 2° C × 3 hours)

= (- 8° C) + (- 6° C)

= - 14° C

So, at 12 midnight the temperature will be - 14° C.

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Step-by-step explanation:

Answer 2

Answer:  -10°C

Step-by-step explanation:Temperature of the room at 9 am = 20°C

9am to 12 noon=3 hours

Temperature increase till 12 noon=3*2=6°C

Temperature of the room at 12 noon=20+6=26°C

12 noon to 12 midnight=12 hours

Temperature decrease till 12 midnight=12*3=36°C

Temperature of the room at 12 midnight=26-36

                                                                  =-10°C