calculated true & false

calculated true & false

by david benedetto -
Number of replies: 3
hello, i'm trying to quiz my students on divisibility rules using a wildcard.

how do i get the answer to calculate whether a randomly generated number is divisible by a specific divisor.

e.g. is the number {n} divisible by 2?

is the mod function available? if so, how does it work in the calculated answer box?

how do i set the correct response based on the calculated answer (T or F)?

i'm using 1.9.2

thoughtful

david benedetto
sausd
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In reply to david benedetto

Re: calculated true & false

by Santiago Ramirez -
Hello David, you can try this:

is the number {n} divisible by {m}?

The formula that you can use is similar to

is_infinite(log(2/(fmod({n},{m}))))

Then, when {n} is divisible by {m} fmod({n},{m})=0 and is_infinite(log(2/(fmod({n},{m}))))=1. Any other case the result is 0.

The correct response is 1 (YES) or 0 (NOT).

You must choose correctly de set of datas (Decimals places = 0)

Sorry but my english is not very good triste.

Santi
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In reply to Santiago Ramirez

Re: calculated true & false

by david benedetto -
thank you.

i finally realized that "is_infinite(log(2/(fmod({n},{m}))))" was the only line in the calculated answer formula line.

i also changed {m} to a constant so i could test their skills with specific divisors.

however, i am getting a division by zero error (below) in the problem even though the problem works perfectly.

Warning: Division by zero in /home/virtualm/public_html/moodle/question/type/calculated/questiontype.php(877) : eval()'d code on line 1
is the number 6088 divisible by 2?

this error shows up only sporatically. if i preview the question several times it doesn't show up each time. i generated 50 problems from 10 to 9999. in the list none of them show any errors and all are working perfectly.

david big grin

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In reply to david benedetto

Re: calculated true & false

by Pierre Pichet -
I have done the same tests and obtain the same warning.
If I look further in the code the fmod() function is used although it is not in the list of allowed functions.
I added this to MDL-18141

Pierre
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