Try harder, ninja JackLevel pending
Jack aspires to become a ninja. In order to achieve that, he climbs a 100-metre pole everyday. However, since he is still young, for every 5 metres he climb, he slides down 3 metres. Assuming (i) it takes him 1 min to climb 1m and 30 secs to slide down 3m, (ii) He only slides down when he climbs exactly 5 metres, how long does it take for him (in minutes) to reach the top?