1. Explain any encryption- decryption technique. Use it to encrypt and decrypt ‘INDIA IS MY
COUNTRY’.
2. Make a grid of natural numbers from 400-500. Find all the prime numbers in the grid. Identify all pairs of twin primes in the grid that you have made. Can all the prime numbers identified by you in the grid be represented as 6n-1 or 6n+1, where n is a natural number? Justify your answer.
3. Let p be any prime number and a&b be any two natural numbers. Justify what all possible values a and b take to satisfy
I.
II. = 1
III. = p2
IV. = 5
V. = 1
where ab means a multiplied by b.
4. Categorize following into Primary and Secondary data sources:
(i) Official Websites
(ii) Magazines
(iii) Newspaper
(iv) Journals
(v) Telephone
(vi) Interview
(vii) Questionnaire
(viii) Survey
(ix) Official Reports
(x) Internet
5. Justify your choice of mean, mode or median in the following cases:
I. A shopkeeper needs to stock his shop with different brands of chocolates. He does a survey in his locality about the preferences of people and needs to decide the brand for which he should place maximum order.
II. Suppose an N.G.O. wants traffic light to be put up at a crossing. They collect data of number of cars passing the crossing on each day and needs to convince the appropriate authority.
