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CBSE Class 12 Computer Science Question 94 of 105

Python Revision Tour — Question 20

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20
Question

Question 6

Is the loop in the code below infinite? How do you know (for sure) before you run it?

m = 3
n = 5
while n < 10:
    m = n - 1
    n = 2 * n - m
    print(n, m)
Answer

The loop is not infinite. To know this without running it we can analyze how n is changed inside the loop in the following way:

n = 2 * n - m

Substituting value of m from m = n - 1,

    n = 2 * n - (n - 1)
⇒ n = 2 * n - n + 1
⇒ n = 2n - n + 1
⇒ n = n + 1

Therefore, inside the loop n is incremented by 1 in each iteration. Loop condition is n < 10 and initial value of n is 5. So after 5 iterations, n will become 10 and the loop will terminate.