Failing a test case - Simple loop and math question.

Question

Here is the question:
Create a function, that will for a given a, b, c, do the following:

Add a to itself b times.
Check if the result is divisible by c.

Notes:
In the first step of the function, a doesn't always refer to the original a.
"if the result is divisible by c", means that if you divide the result and c, you will get an integer (5, and not 4.5314).
The second test is correct.
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My code:
public class Challenge {
public static boolean abcmath(int a, int b, int c) {
int sum = 0;
for (int i = 0; i < b; i++){
sum += a;
if (sum % c == 0) return true;
} return false;
}
}

Failing this unit test and can't figure out why:
@Test
public void test2() {
assertEquals(false, Challenge.abcmath(69, 15, 9));
}
As stated in the notes, second test is correct.
Passes all other 7 tests.

Any thoughts? TIA!!!

Answer 1

Look here:

https://code.sololearn.com/cBRqLTKhiF59/?ref=app

Answer 2

You never changed a and always only added the same a to the sum == a * b.

Answer 3

Oh I see...Thanks so much for your help! : )

Answer 4

I guess you should check the modulo of c AFTER your loop...

Answer 5

Btw. the result of 69*15 is 1035 which is equal to 115*9, so the expected value in your test case is wrong.

Answer 6

Thanks for your reply Sandra. I will try divisibility after loop.

It's not a * b, it's adding a to itself b times. Like this one

abcmath(42, 5, 10) ➞ false
// 42+42 = 84, 84+84 = 168, 168+168 = 336, 336+336 = 672, 672+672 = 1344
// 1344 is not divisible by 10

Answer 7

Then your loop content is wrong. You're calculating a * b.