15.2 practice problem

Question

While loops only
You are given a program that outputs all the numbers from 0 to 20.
Change the code to make it output only numbers that are multiples of 3.

My code:
cin << number;
While( number <= 20)
{
Number = ( number +1)*3;
Cout >> number;
}

Answer 1

1.You have the << and >> operators mixed up.
You need to use cin>> and cout<<.
2.You need to increment number in the while loop. Just add number++; in the loop.
3.You don't need to add one two number in the loop(that's probably the increment attempt, i think)
P.S. you can do cout<<number*3; directly.
Hope this helps :)

Answer 2

Spotted some more problems, besides incomplete code and wrong casing:
You are stopping too late, because output is after increment without checking.

Also use correct indention and post code as a link please like this:

https://code.sololearn.com/cmNM4W6vig7C/?ref=app

Answer 3

salem num goes up to 20 and only for output you are multiplying by 3. That's why it stops at 60

Answer 4

salem

You are doing wrong. You have get those numbers which are multiple of 3 so to check multiple of 3 use modulus operator (%).

You code should be look like this

#include <iostream>
using namespace std;

int main() {
//change the code
int num = 1;

while(num < 20) {
if (num % 3 == 0)
cout << num << endl;

num++;
}

return 0;
}
// This is what I got but I still need it to stop at 20, it just keeps going

Answer 5

You are multiplying the number(+1) by 3 each iteration, giving you the sequence 0, 3, 12, 39, 120, 363, ...

You want 0, 3, 6, 9, ...
So from each step to the next you have to ADD 3.

Do you really need input? The description doesn't say so

Answer 6

int main()
{
//change the code
int num = 0;
while(num < 20)
{
num ++;
cout<<num*3<< endl;
}

return 0;
}
// This is what I got but I still need it to stop at 20, it just keeps going

Answer 7

include <iostream>
using namespace std;

int main()
{
//change the code
int num = 1;
while(num<=20){

num ++;
cout<<num*3<<endl;
}

return 0;
}
how can I make it stop at 20, also why does it print from 3 to 63 why doesnt it stop at my condition

Answer 8

i got it, instead of num<20, it should be 6. since we are multiplying num

Answer 9

hi