Rotate clock's hour hand along with minute hand - ios

Question

I am using CALayers to make an analog clock. The real-time clock works perfect and all the hands are moving smoothly just like default clock app icon in iOS. However, when I try to move the clock hands by touch/dragging, the minute hand moves perfectly but the hour hand doesn't. I am trying to move the clock hands just as they move in a real gear-based clock. Any solutions on how to calculate the angle for hour hand with respect to the movement of minute hand both clockwise and counter-clockwise? Actually I want somewhat similar functionality to this app https://itunes.apple.com/us/app/bb-teaching-clock/id612261763?mt=8
Here is the code for minute hand rotation
float dx = touchPoint.x - minHand.position.x;
float dy = touchPoint.y - minHand.position.y;
deltaAngle = atan2f(dy,dx);
startTransform = minHand.transform;
float angleDifference;
float dx = pt.x - minHand.position.x;
float dy = pt.y - minHand.position.y;
float ang = atan2f(dy,dx);
angleDifference = deltaAngle - ang;
minHand.transform = CATransform3DRotate(startTransform, -angleDifference,0 ,0 ,1);
NSLog(#"angleDifference: %f", angleDifference);
CGFloat hourAngle = (1/12)*(angleDifference);
// hour hand should move in the same direction as minute hand but at a much slower rate
hourHand.transform = CATransform3DRotate (hourHand.transform, -hourAngle, 0, 0, 1);

Answer 1

Try making the following changes, where centerPoint is the center of the clock...
float dx = touchPoint.x - centerPoint.x;
float dy = touchPoint.y - centerPoint.y;
deltaAngle = atan2f(dy,dx);
startTransform = minHand.transform;
float angleDifference;
dx = minHand.position.x - centerPoint.x;
dy = minHand.position.y - centerPoint.y;
float ang = atan2f(dy,dx);
angleDifference = ang - deltaAngle;