Dũng wants to complete the shown arrangement of identical small cubes into a large cube, using as few additional cubes as possible. How many cubes must he add?
Place 1,2,…,9 in the nine cells, once each. Add the horizontal row and the vertical column, then add those two sums. Dung obtains the largest possible result. What is it?
Xuân Lan is 9, her brother 3, and their mother 33. In how many years will the mother be twice the sum of the children’s ages, when the family plans to travel?