What is a negative step for?

It walks data backwards, for example from the last position to the first.

How do you count while rounds?

Look at the change per round and the limit, so adding 3 to pass 20 takes seven rounds.

S5 ICT Programming Loops, Paper 2: steps, conditions and counts

2026-11-02

Paper 2 covers range(0, 7) printing seven lines, a total of 210 from 1 to 20, five rounds with a step of minus 2 and a while loop adding 3 to reach 21, then seven multiples of 4 up to 30, twenty nested iterations, an even sum of 650, sixteen Collatz steps from 7 and a squares loop ending at 16.

Reminders　A range step may be negative, a while loop ends on its condition rather than a limit, and squares are written as i times i.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1
Chapter	Chapter: S5 ICT: Programming Loops in Python
Level	S5

02　Questions (10 items)

FoundationHow many lines does `for i in range(0, 7): print(i)` print?
FoundationWith `total = 0` and `for i in range(1, 21): total += i`, what is total at the end?
FoundationHow many times does `for i in range(10, 0, -2)` iterate?
Foundation`count = 0` then `while count is less than 20: count += 3`. What is count when the loop ends?
IntermediateIn `for i in range(1, 31): if i % 4 == 0:`, how many times is the condition true?
IntermediateIn the nested loops `for i in range(4): for j in range(5):`, how many inner iterations in total?
Intermediate`s = 0` then `for i in range(1, 51): if i % 2 == 0: s += i`. What is s?
ChallengeStarting at n = 7, repeat halving when even and 3n + 1 when odd until n = 1. How many steps?
Challenge`for i in range(1, 5): print(i * i)` prints how many lines, and what is the last one?
Error redoError repair: a student said `sum(range(5))` is 1 plus 2 plus 3 plus 4 plus 5, giving 15. What is the real total?

03　Answers and one-line notes

#	Answer	One-line note
1	7 lines (0 to 6)	range(0, 7) starts at 0 and stops before 7, so it prints 0 to 6, seven numbers in total.
2	210	Summing 1 to 20 gives 210 because range(1, 21) covers exactly the twenty numbers 1 to 20.
3	5 times	A step of minus 2 gives 10, 8, 6, 4 and 2; the next value 0 is not above the stop, so there are 5 rounds.
4	21 (7 rounds)	Adding 3 each round gives 3, 6, 9, 12, 15, 18 and then 21, where the condition finally fails.
5	7 times	The multiples of 4 from 1 to 30 are 4, 8, 12, 16, 20, 24 and 28, seven in all.
6	20	The outer loop runs 4 times and the inner loop 5 times each round, so 4 times 5 gives 20.
7	650	The even numbers from 1 to 50 add to 650, since 25 pairs average 26.
8	16 steps	The chain 7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1 takes 16 steps.
9	4 lines, the last is 16	The squares of 1 to 4 are 1, 4, 9 and 16, so four lines end with 16.
10	10 (0 to 4)	range(5) starts at 0, so the terms are 0, 1, 2, 3 and 4, and the total is 10.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

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