Question 23
The distance between A and B is 7 km. At the beginning, both Gregory and Catherine are at A. Gregory walked from A to B at a constant speed. After Gregory had walked for 1 km, Catherine discovered that he had left his belongings at A. She immediately ran after him at a constant speed of 4 km/h. After handing over the belongings to Gregory, she turned back and started running towards A at the same speed. Given that both Catherine and Gregory reached A and B respectively at the same time, what was Gregory’s speed? Enter the speed in km/h.