Answer:
(i) -34° C.
(ii) The temperature had fallen by 11° C.
Explanation:
(i) As it's a negative number its like we are adding it so 23 + 11 = 34 and as it is a negative number it would be -23 - 11 = -34 which makes it -34° C.
(ii) We know that the temperature now is -45° C, we need to find out how much the temperature had fallen in the 4 hours which had passed. So what we do is essentially add it considering its a negative number so we add -34 by 11 which equals -45. We do this so we can find out how much the temperature had dropped within the 4 hours and as we know that we needed to add 11 to the previous temperature (-34° C) it means that the temperature has dropped by 11° C.