The average of a list of integers goes up by 2 when 25 is added to the list. If 5 is added to the new list, then the average reduces by 1. How many numbers were there in the original list?

A shopkeeper sells two qualities of coffee at the rates of €60 per kg. and €44 per kg, gaining 20% and 10% profit respectively. If he mixes the two variants in the ratio 4:1 and sells the mixture at €36 per kg., what is his gain or loss?

In a trapezoid of area 96 cm^{2}, the length of two parallel sides are in ratio 5:3. If the height of trapezoid is 6 cm, find the length of smaller of the two parallel sides.

A water tank has two types of taps (type-A and type-B). A tap of type-A can fill the tank in 72 minutes, while a tap of type-B can fill the same tank in 96 minutes. If there are 3 type-A taps and 4 type-B taps that can be used to fill the tank, how long will it take to fill an empty tank?