A variable name in certain computer language must be either an alphabet or an alphabet followed by a decimal digit. The total number of different variable names that can exist in that language is equal to a. `280` b. `390` c. `286` d. `296`

Fifteen identical balls have to be put in five different boxes. Each box can contain any number of balls. The total number of ways of putting the balls into the boxes so that each box contains at least two balls is equal to a. .^9C_5 b. .^10 C_5 c. .^6C_5 d. .^10 C_6

A person predicts the outcome of 20 cricket matches of his home team. Each match can result in either a win, loss, or tie for the home team. Total number of ways in which he can make the predictions so that exactly 10 predictions are correct is equal to a. ^20 C_(10)xx2^(10) b. ^20 C_(10)xx3^(20) c. ^20 C_(10)xx3^(10) d. ^20 C_(10)xx2^(20)

Total number less than 3xx10^8 and can be formed using the digits 1, 2, 3 is equal to a. 1/2(3^9+4xx368) b. 1/2(3^9-3) c. 1/2(7xx3^8-3) d. 1/2(3^9-3+3^8)

Total number of six-digit numbers that can be formed having the property that every succeeding digit is greater than the preceding digit is equal to a. ^9C_3 b. ^10 C_3 c. ^9p_3 d. ^10 p_3

Two players P_1a n dP_2 play a series of 2n games. Each game can result in either a win or a loss for P_1dot the total number of ways in which P_1 can win the series of these games is equal to a. 1/2(2^(2n)-^ "^(2n)C_n) b. 1/2(2^(2n)-2xx^"^(2n)C_n) c. 1/2(2^n-^"^(2n)C_n) d. 1/2(2^n-2xx^"^(2n)C_n)

Write the following sets in roster form (i) B= {x:x is a natural number smaller than 6} (ii) C= {x:x is a two-digit natural number such that the sum of its digits is 8). (iii) D= {x : x is a prime mimber which is a divisor of 60}. (iv) E= {x:x is an alphabet in BETTER}.

Which of the following sets are equivalent or unequal or equal sets? (i) A=The set of vowels in the Englisht alphabets. B=The set of all letters in the word "VOWEL". (ii) C={2,3,4,5} D={x : x in W, 1 lt x lt 5} (iii) X={" x : x is a letter in the word LIFE"} Y={F,I,L,E} (iv) G={"x : x is a prime number and 3 "lt x lt 23} H={x : x is a divisor of 18}