Question

Given here is an algorithm to swap two numbers. Which of the following line will replace'?" to complete the algorithm?
Step 1: Read two numbers $X$ and $Y$.
Step 2: ?
Step 3: $Y=X-Y$
Step 4: $X=X-Y$

• A. $X=X+Y$
• B. $X=X\times Y$
• C. $X=\frac{X}{Y}$
• D. $X=X-Y$

Answer 1

The correct option is A $X=X+Y$

Suppose value of $X=10$ and $Y=20$
$X=X+Y\to X=10+20=30$
$Y=X-Y\to Y=30-20=10$
$X=X-Y\to X=30-10=20$
Now $X=20$ and $Y=10$.