Aptitude and Reasoning Questions

Given total number of students in the class = 21

So each student will have 20 greeting cards to be send or receive (21 - 1(himself))

Therefore, the total number of greeting cards exchanged by the students = 20 x 21 = 420.

Given digits are 0, 4, 2, 6

Required 4 digit number should be greater than 6000.

So, first digit must be 6 only and the remaining three places can be filled by one of all the four digits.

This can be done by

1x4x4x4 = 64

Greater than 6000 means 6000 should not be there.

Hence, 64 - 1 = 63.

Given,721+722+723+724

721(1 + 7 + 49 + 343)
721(400)

Now, 400 is divisible by 25. The remainder will be 0

As these three strategies P, Q and R are independent so these will cut cost one after the other.
If initial cost is Rs 100, then
20% cost is cut after initializing strategy P, then cost will remain 80% = 80
further 30% cost is cut after strategy Q, then cost will remain 70% of 80 = 56
further 10% cost is cut after strategy R, then cost will remain 90% of 56 = 50.4

Thus final cost remains 50.4 % of the original cost. Hence net saving is 100 - 50.4 = 49.6 %.

In all other pairs, second is the place of stay of the first.

There are 5 slots.

                   __ __ __ __ __

The first slot must be a four. There are 4 ways to put a four in the first slot.

There are 4 ways to put a five in the second slot, and there are 4 ways to put a six in the third slot. etc.

(4)(4)(4)(4)(4) = 1024

Therefore there are 1024 different ways to produce the desired hand of cards.

Here in 2nd column if you add the individual digits

 we get  3 + 7 + 0 =10 , 2 + 2 + 4 = 8 , 7 + 3 + 0 = 10

7   10   3  --> 7+3 =10

6   8     2  --> 6+2 =8

x   10   1  --> x+1 =10

Here we can observe that by adding 1st and 3rd column elements we get 2nd column elements

 --> x = 9