The question!

My memories up to the age of 10 or 11 are greater than the later years. Our family is a big one, with a total of 7 sisters and 4 brothers. We are spaced almost equally with a gap of two years. The four of us - the brothers, were in school. The two elder brothers, though having age difference, were in the same class ...I wonder how! I was 2 classes lower to my elder brother, and my younger brother was two classes lower to me.
At home, we used to have a lot of fun, playing, fighting ...and what not? On many occasions, we tested our knowledge by quizzing, asking mental maths etc.

On one occasion, my younger brother, who was 6 years old, came up with a question to my elder brothers. He was fresh with his maths class, where he was taught to find out the sum of 1 item, given the price of 4 items. He challenged my elder brother to solve a problem. He simply asked, 'What is the price of one mango?', without knowing that it was only a part of the sum. When my elder brother replied, 'How do I know?', my younger brother teased him by saying that he, being in an elder class, didn't know the simple sum which he knew. The elder one got wild, and slapped him on hid cheek. Poor chap ....he didn't know why he was beaten!