The average age of a class of 6 girls is x years. Four new girls having ages x – 2, x + 2, x + 4 and x + 6 joins the class. What is the new average age (in years) of the class?
Identical cubes of largest possible size are cut from a solid cuboid of size 65 cm × 26 cm × 3.9 cm. What is the total surface area (in cm2) of all the small cubes taken together?