19.
A mobile number consists of ten digits. First four digits are 9,9, 7 and 9. Make the smallest mobile number by using only one digit twice from 7, 2, 5, 8, 0.
20.
Along a highway, there are teak tree on one side of the highway and neem on the other side. The teak trees are separated by 10 m and the neem trees are separated by 36 m. If an teak and a neem trees are both present at the point where the highway begins, after how much distance along the highway will they both be in front of each other again?