qt - decimals and round up to whole numbers

Question

This is what I've got so far but I can't figure out my next steps.

When I divide my value with 3 I get whole numbers but I want it to display with one decimal and I don't know how.

When that's done I want to round the decimal up or down depending on its value. If it's 3.5 or over it should become 4 and if it's 3.4 or under it should be 3.

void MainWindow::on_pushButton_clicked(){

int paragraph = ui->lineEdit->text().toInt();
int section = ui->lineEdit_2->text().toInt();
int lines = ui->lineEdit_3->text().toInt();

int sum = (paragraph * (lines + 1) -(section * lines));

ui->label_4->setText(QString::number(sum/3));
}

Answer 1

You are dividing integrers and therefore get integer. So fractional part is truncated.

int a = 11;
a = a / 3;        // a is 3 now

double b = 11;
b = b / 3;        // b is 3.6666... now

double c = a / 3; // c is 3 now
c = b / 3;        // c is 3.6666... now

Return type of operators like +, -, * or / is determined by first object in there.

Just use qRound(double(sum)/3.0) or qRound(double(sum)/3) to get rounded value.

If you want to display result with 1 decimal, use QString::number(double(sum)/3.0, 'f', 1).

Please study C basics (read critical parts of K&R) before using C++. And study C++ before using Qt.