Mathematics - Online Test

Q1. Two matrices A and B are multiplicative inverse of each other only if
Answer : Option C
Explaination / Solution:

If AB = BA = I , then A and B are inverse of each other. i.e. A is invers of B and B is inverse of A.

Q2. The number of ways, in which a student can select one or more questions out of 12 each having an alternative, is
Answer : Option B
Explaination / Solution:

Since a  student can solve each question in 3 different ways - either   he can attempt the  first alternative ,or the second alternative or he can leave it unanswered.

Hence number of ways in which a student can attempt one or more of the 12 given questions =

Now we can consider a case that the student leave all the 12 given questions unanswered.

The number of ways, in which a student can select one or more questions out of 12 each having an alternative= 

 


Q3. is equal to 
Answer : Option C
Explaination / Solution:

ddx(log|x|)=1|x|x|x|=x|x|2=xx2=1x
Q4. In the following case, determine whether the given planes are parallel or perpendicular, and in case they are neither, find the angles between them. 2x – y + 3z – 1 = 0 and 2x – y + 3z + 3 = 0
Answer : Option B
Explaination / Solution:

We have , 
2x – y + 3z – 1 = 0 and 2x – y + 3z + 3 = 0 . Here ,

Therefore , the given planes are parallel.

Q5. is
Answer : Option B
Explaination / Solution:



Q6. Differential equation of the family of ellipses having foci on y-axis and centre at origin is
Answer : Option A
Explaination / Solution:



Q7. The coefficients of  in the expansion of  , where n is an even integer is
Answer : Option D
Explaination / Solution:



Q8. If a set A has n elements then the total number of subsets of A is
Answer : Option C
Explaination / Solution:

The total no of subsets=2n

Q9.  
Answer : Option D
Explaination / Solution:



Q10.

A dietician wishes to mix together two kinds of food X and Y in such a way that the mixture contains at least 10 units of vitamin A, 12 units of vitamin B and 8 units of vitamin C. The vitamin contents of one kg food is given below:

Food

Vitamin A

Vitamin B

Vitamin C

X

1

2

3

Y

2

2

1

One kg of food X costs Rs 16 and one kg of food Y costs Rs 20. Find the least cost of the mixture which will produce the required diet?

Answer : Option A
Explaination / Solution:

Let number of kgs of food of brand X = x
And number of kgs. of food of brand Y = y
Therefore , the above L.P.P. is given as :
Minimise , Z = 16x +20y , subject to the constraints : x + 2y ≥ 10,2x + 2y ≥12,3x + y ≥8,x,y ≥ 0.,

 

Corner points

Z =16x +20 y

C(10 , 0 )

160

 

B (0,8)

160

D(1,5 )      

116

A(2,4)

112……………..(Min.)


Here Z = 112 is minimum.
i.e. Least cost of the mixture is Rs 112 (2 kg of Food X and 4 kg of food Y).