Train X takes 21 hours to travel from station A to station B, while train Y takes 28 hours to travel from station B to station A. If train X and Y starts at same time from stations A and B respectively, after what time will they cross each other? (Assume trains travel with uniform speed)
The cost of a doll is a two digit number (for example ฿xy). Its selling prices has same digits as cost with digits interchanged (฿yx). If its profit margin is divided by 9, find the remainder of division.
A shopkeeper sells two qualities of sugar at the rates of ฿33 per kg. and ฿42 per kg, gaining 10% and 20% profit respectively. If he mixes the two variants in the ratio 1:4 and sells the mixture at ฿40.8 per kg., what is his gain or loss?