Question

Add the following expressions:
8mn, -3mn, -2mn, 5mn.

Answer 1

Hint: Addition is one of the four basic fundamental operators subtraction, multiplication, division etc. there are various properties of addition that has to be taken care of before performing addition. Same is the way of carrying out any other operation.

Complete step-by-step answer:
We observe that the following expressions to be added are not only positive but two of them are negative in nature. We must be aware of the fact that when two positive numbers are added it yields a positive number but when two negative numbers are added it yields a negative number only.
One may understand it from the way that since the negative sign is common in both the numbers it can be taken out in common and the rest of the digits left can be added in a bracket and then be assigned with the negative sign at last.
We must be careful while adding the terms because only like terms can be added that is the terms with like units if the units of the numbers to be added are different then it is converted so that all the numbers to be added have the same unit. Since the above terms have the same unit therefore they can be added easily.
Let us add all the positive terms first,
$
  \Rightarrow 8 - 3 - 2 + 5 \\
  \Rightarrow 8 + 5 - 3 - 2 = 13 - 3 - 2 \;
$
Now let us take the negative sign common and add it,
$
  \Rightarrow 13 - (3 + 2) \\
  \Rightarrow 13 - 5 = 8 \;
$
Hence the correct answer is 8mn.
So, the correct answer is “8mn”.

Note: One must note that if a number greater in magnitude is added to a number smaller in magnitude then the resultant number has the sign similar to the sign of the number greater in magnitude. Therefore one can get a negative number despite adding two numbers.