Addition of integers on a number line
(i)     Let us add 3 and 5 on number line. On the number line, we first move 3 steps to the right from 0 reaching 3, then we move 5 steps to the right of 3 and reach 8. Thus, we get 3 + 5 = 8

(ii)     Let us add – 3 and – 5 on the number line. On the number line, we first move 3 steps to the left of 0 reaching – 3, then we move 5 steps to the left of – 3 and reach – 8.
Thus, (– 3) + (– 5) = – 8.
We observe that when we add two positive integers, their sum is a positive integer. When we add two negative integers, their sum is a negative integer.

(iii)     Suppose we wish to find the sum of (+ 5) and (– 3) on the number line. First we move to the right of 0 by 5 steps reaching 5. Then we move 3 steps to the left of 5 reaching 2. Thus, (+ 5) + (– 3) = 2
(iv)     Similarly, let us find the sum of (– 5) and (+ 3) on the number line. First we move 5 steps to
the left of 0 reaching – 5 and then from this point we move 3 steps to the right. We reach the point – 2.
Thus, (– 5) + (+3) = – 2. 