some MCQs

Q17: Given: a = i + j + k, a. b = 1 and a × b = j - k. Then, b is equal to
A. -2i
B. 2i + k
C. 3j
D. i

Q18: Consider points A , B , C and D with position vectors 7 i – 4 j + 7 k , i
– 6j + 10 k, –i , 3j + 4k and 5i – j + 5k respectively. Then ABCD is a
A. Rhombus
B. Rectangle
C. Parallelogram but not a rhombus
D. None of Above

Q22: If Rank of a matrix is equal to No. of variable then it have
A. Non-Trivial solution, x = y = z? 0
B. Trivial Solution, x = y = z = 0
C. x = y = 0, z = 0
D. None
Q25: If 42 men can do a work in 15 days, how many men are required to
complete it in 21 days?
A. 24
B. 36
C. 30
D. None of these


Q27: The sum of all possible two digit number formed from three different
one digit natural number when divided by the sum of the original three
number is equal to:?
A. 18
B. 22
C. 36
D. None of these

Q29: There are four prime no written in ascending order. The product of the
first three is 385 and that of the last three is 1001.The last no is?
A. 11
B. 13
C. 17
D. 19

Q30: A school committee of 2 teachers and 4 students. The number of
different committees that can be formed from 5 teachers and 10
students is:
10
15
2100
D. 8
Q31: You are having 31kg of rice. You are provided with a 1kg stone for
weighing. In how many weights the 31kg of rice can be weighed.
A. 6
B. 34
C. 63
D. 5

Q32: L.C.M & H.C.F. The L.C.M. (Lowest (or Least) Common Multiple) of two
numbers is 45 times to their H.C.F (Highest Common Factor). If one of
the numbers is 125 and sum of L.C.M. and H.C.F. is 1150, the other
number is:
A. 215
B. 220
C. 225
D. 235

Q35: The sum of the three prime no is 100.If one of then exceed another by
36, then one of the?
A. 7
B. 29
C. 41
D. 67

Q37: When a number is divided by 13, the remainder is 11.When the same
number is divided by 17; the remainder by 9.What is the number?
A. 339
B. 349
C. 369
D. Data inadequate



i know the answers but i dont know hoe it comes.
plz help.
Q40: Thirty men take 20 days to complete a job working 9 hours a day. How
many hours a day should 40 men work to complete the job?
A. 8 hrs
B. 7.5 hrs
C. 7 hrs
D. 9 hrs