if Statements: Practice Questions (Computer Science A 2.3)

These are original Marlbridge practice questions, not past exam questions. All scenarios are fictional. Mark points are a suggested Marlbridge rubric, not an official scoring guideline. Assume every code segment compiles unless a question says otherwise, and that no calculator is allowed.

Question 1 (multiple choice · foundation)

What is printed?

int x = 7;
if (x > 10) {
    System.out.println("A");
} else {
    System.out.println("B");
}
System.out.println("C");

(A) A
(B) B
(C) B then C
(D) A then C

Answer and explanation

Answer: (C). 7 > 10 is false, so the else body prints B. The statement after the if-else always runs, so C is printed next.

(A) assumes the condition is true.
(B) forgets that the last println is outside the if-else and always runs.
(D) combines the wrong branch with the right final statement.

Question 2 (multiple choice · core)

What is printed?

int n = 8;
if (n > 5) {
    System.out.print("X");
}
if (n > 7) {
    System.out.print("Y");
}
if (n > 9) {
    System.out.print("Z");
}

(A) X
(B) XY
(C) XYZ
(D) Y

Answer and explanation

Answer: (B). The three if statements are independent. 8 > 5 is true (X), 8 > 7 is true (Y), 8 > 9 is false (Z is skipped). The output is XY.

(A) stops after the first true condition, which is what an if-else-if chain would do (Topic 2.4), not separate ifs.
(C) ignores the third condition.
(D) prints only the last true condition.

Question 3 (multiple choice · core)

What is the value of n after the code runs?

int n = 20;
if (n > 15) {
    n = n - 8;
}
if (n > 10) {
    n = n - 8;
}

(A) 4
(B) 12
(C) 20
(D) 6

Answer and explanation

Answer: (A). First if: 20 > 15 is true, so n becomes 12. Second if is tested on the new value: 12 > 10 is true, so n becomes 4.

(B) applies only the first if, forgetting the second condition uses the updated n.
(C) assumes neither body runs.
(D) is not reachable by either path (20 - 8 - 8 is 4); it comes from subtracting 14.

Question 4 (multiple choice · core)

What is printed?

int score = 3;
if (score > 5);
{
    System.out.println("High");
}
System.out.println("End");

(A) End
(B) High
(C) High then End
(D) The code does not compile.

Answer and explanation

Answer: (C). The semicolon after the condition is an empty statement that is the whole body of the if. The braces that follow form a plain block that always runs. So High is printed, then End.

(A) is what the programmer intended, but the stray semicolon makes the block unconditional.
(B) forgets the final statement.
(D) is wrong: an empty statement and a block are both legal Java.

Question 5 (multiple choice · core)

What is printed?

int k = 1;
if (k > 3)
    System.out.println("P");
    System.out.println("Q");
System.out.println("R");

(A) nothing
(B) R
(C) Q then R
(D) P then Q then R

Answer and explanation

Answer: (C). Without braces only the single statement directly after the condition (println("P")) belongs to the if. Since 1 > 3 is false, P is skipped. Q and R are not part of the if, so both are printed.

(A) and (B) assume Q is inside the if because it is indented.
(D) ignores that the condition is false.

Question 6 (multiple choice · core)

Which code segment always has the same effect as the following?

if (x > 3) {
    s = "big";
} else {
    s = "small";
}

(A) if (x < 3) { s = "small"; } else { s = "big"; }
(B) if (x <= 3) { s = "small"; } else { s = "big"; }
(C) if (x > 3) { s = "big"; } if (x < 3) { s = "small"; }
(D) if (x >= 3) { s = "big"; } else { s = "small"; }

Answer and explanation

Answer: (B). The original gives “small” for every x that is not greater than 3, that is, for x <= 3. Swapping the branches and reversing the condition to its exact complement gives (B).

(A) mishandles x = 3: the original gives “small” for 3, but (A) gives “big” because 3 < 3 is false.
(C) leaves s unchanged for x = 3, because neither condition is true.
(D) gives “big” for x = 3, which differs from the original.

Question 7 (multiple choice · stretch)

What is printed?

int a = 5;
int b = 12;
boolean ok = b % a == 2;
if (ok) {
    a = a + b;
} else {
    a = a - b;
}
if (a > 10) {
    b = b / 2;
}
System.out.println(a + " " + b);

(A) 17 6
(B) -7 12
(C) 17 12
(D) -7 6

Answer and explanation

Answer: (A). b % a is 12 % 5 = 2, so ok is true and a becomes 5 + 12 = 17. The second condition 17 > 10 is true, so b becomes 12 / 2 = 6. Output: 17 6.

(B) takes the else branch and skips the second body.
(C) takes the correct first branch but forgets the second selection.
(D) takes the else branch (a = -7) and wrongly still halves b.

Question 8 (constructed response · core)

A courier charges 5.00 dollars for a parcel of 10 kg or less, and 12.50 dollars for a heavier parcel. A parcel marked “fragile” has 3.00 dollars added to the cost.

(a) Write a Java method shipping with the header public static double shipping(double kg, boolean fragile) that returns the cost. (5 marks)

(b) Give the value returned by shipping(10, true) and shipping(10.5, false). (2 marks)

Answer and explanation

(a) Model answer.

public static double shipping(double kg, boolean fragile) {
    double cost;
    if (kg <= 10) {
        cost = 5.00;
    } else {
        cost = 12.50;
    }
    if (fragile) {
        cost = cost + 3.00;
    }
    return cost;
}

(b) shipping(10, true): 10 <= 10 is true, so cost is 5.0, and fragile adds 3.0, giving 8.0. shipping(10.5, false): 10.5 <= 10 is false, so cost is 12.5, and no surcharge: 12.5.

Suggested Marlbridge rubric (7 marks).

Marks	Awarded for
1	Correct method header and a return of type `double`
1	Correct boundary: `kg <= 10` for the light parcel (10 kg is light)
1	Two-way selection for the base price, with 5.00 and 12.50 on the correct branches
1	Separate one-way `if (fragile)` adding 3.00, not an `else` of the weight test
1	`cost` has a value on every path and is returned
2	(b): 1 mark for each correct result (8.0 and 12.5)

An answer that uses four nested branches or a different but equivalent structure is correct if it gives the same costs. Penalise kg < 10 (wrong for exactly 10 kg).

Question 9 (constructed response · core)

A student wrote this code to print “Pass” for a mark of 50 or more and “Fail” otherwise. It has three problems.

int mark = 62;
if (mark = 50) {
    System.out.println("Pass")
} else (mark < 50) {
    System.out.println("Fail");
}

(a) Identify the three errors. (3 marks)

(b) Write a corrected version that works for every integer mark. (3 marks)

Answer and explanation

(a) (1) mark = 50 is an assignment, not a comparison, and does not produce a boolean. (2) The statement System.out.println("Pass") is missing its semicolon. (3) else cannot have a condition: else (mark < 50) is not valid syntax.

(b)

int mark = 62;
if (mark >= 50) {
    System.out.println("Pass");
} else {
    System.out.println("Fail");
}

The condition is mark >= 50 because “50 or more” includes 50. The else needs no condition: every other mark fails.

Suggested Marlbridge rubric (6 marks).

Marks	Awarded for
1	Identifies the `=` instead of a comparison
1	Identifies the missing semicolon
1	Identifies the condition after `else`
1	Condition `mark >= 50` (the boundary is included)
1	Semicolon restored
1	A plain `else` with no condition

Question 10 (constructed response · stretch)

Two code segments use a variable points, starting at 8.

Segment 1:

int points = 8;
if (points > 5) {
    points = points + 4;
}
if (points < 10) {
    points = points + 1;
}

Segment 2:

int points = 8;
if (points > 5) {
    points = points + 4;
} else {
    points = points + 1;
}

(a) Find the final value of points after each segment. Show a trace table for Segment 1. (4 marks)

(b) Segment 1 is changed so that the second if becomes an else attached to the first if. Explain in one sentence why this gives the same result as Segment 2. (1 mark)

(c) A student says “the if-else in Segment 2 is just two separate ifs written differently”. Use the two segments (or another example) to show this is false. (2 marks)

Answer and explanation

(a) Segment 1 trace:

Statement	`points` before	Condition	`points` after
first `if`	8	`8 > 5` true	12
second `if`	12	`12 < 10` false	12

Segment 1 ends with 12. Segment 2: 8 > 5 is true, so points becomes 12 and the else is skipped. Segment 2 ends with 12.

(b) An if-else makes a single decision: the else body runs only if the if condition is false, so after the if body ran the second action cannot happen.

(c) The segments agree here only because the second condition happened to be false after the first body changed points. If the second if were points > 10, then in Segment 1 the second body would also run (12 > 10), but in an if-else it would not. Two separate ifs test their conditions one after the other on the updated values; an if-else decides once.

Suggested Marlbridge rubric (7 marks).

Marks	Awarded for
2	Trace table for Segment 1: correct before/after values (1 mark for each row)
1	Segment 1 final value 12
1	Segment 2 final value 12
1	(b) states a single decision / else skipped when the if ran
1	(c) gives a valid counter-example or explains independent testing on updated values
1	(c) correct outcome of the counter-example

How did you do?

Questions 1 to 5 test the central skill: knowing which statements run. If you missed Question 2 or 3, revisit “If-else is not two ifs” in the study guide. If you missed Question 4 or 5, review “Braces and layout” and “The stray semicolon”. Then use the checklist.