Cardiac output = stroke volume × Heart rate ⇒ Cardiac output = 5L or 5000 ml ⇒ Blood volume in ventricles at the end of diastole = 100 ml ⇒ Blood volume in ventricles at the end of systole = 50 ml Stroke volume = 100 – 50 = 50 ml. So, 5000 ml = 50 ml × Heart rate So, Heart rate = 100 beats per minute.