NSInteger numberOfPickers = 3;

CGFloat pickerWidth = self.view.frame.size.width/numberOfPickers;

for(int i =0; i< numberOfPickers; i++) {
    CGRect frame = CGRectMake(i*pickerWidth, 0, pickerWidth, 100);
    UIPickerView *picker = [UIPickerView alloc] initWithFrame:frame];
    [self.view addSubview:picker];
}