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Grade 7 Computer Science — Tracing a loop with a total

Trace a loop that keeps a running total, and say what the total holds once the loop has finished.

Name: ________________________

  1. 1.A program says: set total to 10; repeat 3 times: add 4 to total. What does total hold at the end?

  2. 2.A program says: set total to 1; repeat 4 times: double total. What does total hold at the end?

  3. 3.A program says: set total to 0; repeat 4 times: add 3 to total. Someone answers 3, because 3 was the last thing added. What is wrong with that?

    • a) Nothing is wrong — 3 is right
    • b) The total starts again from nothing each time round
    • c) The loop only ever runs once
    • d) The total keeps everything added before it, so it comes to 12

  4. 4.A program says: set total to 100; repeat 5 times: take 8 away from total. What does total hold at the end?

  5. 5.A program says: set total to 0; repeat 5 times: add 2 to total. After the loop has finished, it prints total once. How many numbers appear on the screen?

    • a) None
    • b) Ten
    • c) One
    • d) Five

  6. 6.A program says: set total to 0; repeat 4 times: add 6 to total. What does total hold at the end?

  7. 7.A program says: set total to 0; repeat 7 times: add 3 to total. What does total hold at the end?

  8. 8.Each of these programs starts with total holding 0. Sort each loop by whether it finishes with total above 30.

    Groups: Above 30 · 30 or below

    • repeat 3 times: add 5 to total
    • repeat 5 times: add 4 to total
    • repeat 4 times: add 9 to total
    • repeat 8 times: add 5 to total
    • repeat 7 times: add 6 to total
    • repeat 2 times: add 8 to total

Answer key — Grade 7 Computer Science — Tracing a loop with a total

  1. 1. 22
  2. 2. 16
  3. 3. d) The total keeps everything added before it, so it comes to 12
  4. 4. 60
  5. 5. c) One
  6. 6. 24
  7. 7. 21
  8. 8. repeat 4 times: add 9 to total → Above 30; repeat 3 times: add 5 to total → 30 or below; repeat 8 times: add 5 to total → Above 30; repeat 2 times: add 8 to total → 30 or below; repeat 7 times: add 6 to total → Above 30; repeat 5 times: add 4 to total → 30 or below