Question

the temperature at 12 noon was 10 above 0 if it decreases at the rate of 3 per hour until midnight at what time would the temperature be 8 below zero


class 7​

Answer 1

Answer :-

The temperature at 12 noon = 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.

Answer 2

Answer:

Step-by-step explanation:  Let noon be time t = 0 hr.,

then the temperature T in degrees Celsius at t hr. would be:

T = 10 - 2t

Now,

To find when the temperature is 8°C below zero,

T = -8

10 - 2t = -8

Thus, the temperature is 8°C below zero at 9:00 pm.

To find the temperature at midnight,

use t = 12:00

T = 10 - 2(12) = 10 - 24 = -14

2T=18

T=9

Thus, the temperature is 8°C below zero at 9:00 pm.

To find the temperature at midnight,

use t = 12:00

T = 10 - 2(12) = 10 - 24 = -14

Thus, the temperature at midnight is 14∘C below zero.