ITPEC FE Subject B April 2024 Question 3
From the answer group below, select the correct answer to be inserted into blank in the program.
The program outputs the even numbers between 1 and 100. Subsequently, it prints the sum of those even numbers. Note that division is performed for data type integer, that is, a ÷ b is the quotient of a divided by b.
Answer group
Explanation
i mod 2 = 0 — a number is even exactly when dividing it by 2 leaves no remainder.
mod gives the remainder, while ÷ here is integer division and gives the quotient. For i from 1 to 100, i mod 2 is 0 for 2, 4, …, 100 and 1 for the odd numbers. So the loop outputs the 50 even numbers and then their sum, 2,550.
Answer (c)
Why not others:
- •(a) —
i ÷ 2is the quotient, which is 0 only fori= 1: the program outputs 1 and a sum of 1 - •(b) — the quotient is non-zero for every
ifrom 2 to 100, so it outputs all of 2 to 100, odd and even - •(d) — a remainder of 1 selects the odd numbers 1, 3, …, 99
- •(e) — true only for
i= 2, so it outputs just 2 - •(f) — true for every
iexcept 2, so it outputs 1 and 3 to 100
Key rule: Test divisibility with the remainder, x mod n = 0, not with the quotient; under integer division the quotient is 0 only when x is less than n.
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