Analytical Questions!

Hello everybody. Well I have come up with quite a tough brain tester for you guys. There are 5 questions which are based on common sense. Some require reasoning and analytical knowledge. Try to solve as many as you can. You'll get a great feeling once you are able to solve them. I am just posting the questions right now and I'll post the answer later when I feel the topic has become old and no more replies are coming in. Best of Luck!

1) Find the missing number: 18, 21, ? , 54, 6

2) Find the next number in the series: 4, 3, 7 ,6, 13, ?

3) Year:1991 --- Nearly two years and a little more from today, Radha's neighbour Alka asked her what her age was on her(i.e Radha's) last birthday? Radha replied that she was 12 years old. " And how old would you be on your next birthday?" Radha replied, "Aunty, if I do not fail in any class I shall be completing 12+3 course and would be studying for M.A. on my next birthday." Alka was puzzled. Could you tell the exact date, month and year on which Alka had asked Radha the above question?

4) You are not called upon to test your skill in the game of cards. It is merely a colour problem. Take a pack of playing cards. You know they are 52 in all. Seperate the Red from the Black. Now give it to me, I have arranged them as under: Pile No.1: There are three times as many blacks as red. Pile No.2: There are three times as many reds as black. Pile No.3: There are twice as many blacks as red. Now, could you tell the number of cards of each colour in each of the three piles?

5) Mystery of Relationship: Lajwanti Devi of village Lajpur was a young , demure and lively woman. Sarita Rani, her neighbour, asked her once, on seeing her with a gentleman, "What is your relationship with the gentleman accompanying you?" Lajwanti replied. "I will neither tell you his name nor my relations with him. I will, however, reveal that his mother-in-law and my mother-in-law are mother and daughter." How were these two related to each other?