ROUND, RANDOM and a trace

A shop rounds a price

• ROUND(Value, Places) returns Value rounded to Places decimal places.
• Places is an integer. ROUND(3.14159, 2) is 3.14. ROUND(9.6, 0) is the whole number 10.
• The syllabus lists ROUND with DIV, MOD and RANDOM.

OUTPUT ROUND(3.14159, 2)
OUTPUT ROUND(9.6, 0)

A dice uses RANDOM

• RANDOM() returns a real from 0 to 1, including both ends. Each run can differ.
• ROUND(RANDOM() * 6, 0) gives a whole number from 0 to 6, so it is not a dice: 0 and 6 also come up only half as often as the others. 1 + ROUND(RANDOM() * 5, 0) gives 1 to 6, though 1 and 6 are still less likely. The paper uses RANDOM when the result may vary, so you are not asked for one fixed output.

OUTPUT ROUND(RANDOM() * 6, 0)

Fill a trace table

• A trace table is a dry run. One row is one pass of the loop. You write the variables after that pass.
• Total starts at 0. After I = 1 it is 1. After I = 2 it is 3. After I = 3 it is 6.

DECLARE I, Total : INTEGER
Total ← 0
FOR I ← 1 TO 3
    Total ← Total + I
    OUTPUT I, " ", Total
NEXT I

Watch out

• Round a half only when you have checked the digit. The tasks here are not on a halfway value.
• RANDOM() is not RAND. RAND belongs to the 9618 guide, not to this syllabus.

Common mistakes

• ROUND takes the value first and the number of places second.
• In a trace, record the values after the line has run, not the values you hope the next line will produce.

Now you try

• The first task is ROUND. The second prints a trace, one row per line.
• Press Check answer to test it.