# Farukh starts to paint a fence on one day. On the second day, two more friend of Farukh join him. On the third day 3 more friends of him join him and so on. If the fence is completely painted this way in exactly 20 days, then find the number of days in which 10 girls painting together can paint the fence completely, given that every girl can paint twice as fast as Farukh and his friends(Boys)?(Assume that the friends of Farukh are all boys)