Procedures, Functions, Arrays and File Handling: Question 9

Syllabus 8.2

Multiple choice 1 mark

A weather monitoring system stores temperature readings, in degrees Celsius, from 3 sensors over 3 days in a two-dimensional array, Readings, declared as ARRAY[1:3, 1:3], where the first index is the sensor number and the second index is the day number. The nested loop below counts how many of the 9 readings are above 25 degrees Celsius.

DECLARE Readings : ARRAY[1:3, 1:3] OF INTEGER
DECLARE Sensor : INTEGER
DECLARE Day : INTEGER
DECLARE Count : INTEGER

Readings[1,1] ← 22
Readings[1,2] ← 27
Readings[1,3] ← 19
Readings[2,1] ← 26
Readings[2,2] ← 24
Readings[2,3] ← 30
Readings[3,1] ← 18
Readings[3,2] ← 25
Readings[3,3] ← 29

Count ← 0
FOR Sensor ← 1 TO 3
    FOR Day ← 1 TO 3
        IF Readings[Sensor, Day] > 25
            THEN
                Count ← Count + 1
        ENDIF
    NEXT Day
NEXT Sensor
OUTPUT Count

What value is output for Count?

Show worked solution Hide worked solution

Step 1: List all 9 readings and check each against the threshold

The outer loop fixes Sensor from 1 to 3; for each sensor, the inner loop checks Day from 1 to 3, testing whether Readings[Sensor, Day] > 25 (strictly greater than):

Sensor	Day	Readings[Sensor,Day]	> 25?	Count after this step
1	1	22	No	0
1	2	27	Yes	1
1	3	19	No	1
2	1	26	Yes	2
2	2	24	No	2
2	3	30	Yes	3
3	1	18	No	3
3	2	25	No (25 is not strictly greater than 25)	3
3	3	29	Yes	4

Step 2: Read off the final value of Count

Four readings exceed 25: 27, 26, 30 and 29. Note that Readings[3,2] = 25 does not count, since the condition uses >, not >=.

OUTPUT Count displays 4, option B.

Final answer

Count = 4, option B

Worked solution

Step 1: List all 9 readings and check each against the threshold

Step 2: Read off the final value of Count

Final answer