Try this:
- (double)scaleFromSliderValue:(double)sliderValue minScale:(double)minScale {
return minScale + sliderValue * (1 - minScale);
}
- (void)sliderValueChanged:(UISlider *)slider {
double scale1 = [self scaleFromSliderValue:slider.value minScale:0.5];
view1.transform = CGAffineTransformMakeScale(scale1, scale1);
double scale2 = [self scaleFromSliderValue:slider.value minScale:0.9];
view2.transform = CGAffineTransformMakeScale(scale2, scale2);
double scale3 = [self scaleFromSliderValue:slider.value minScale:0.35];
view3.transform = CGAffineTransformMakeScale(scale3, scale3);
}