Quantitative Aptitude - Arithmetic Ability 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.

Let the number of correct answers be X.

Number of incorrect answers = (60 – X).

Therefore, 4x – (60 – x) = 130 

=> 5x = 190  => x = 38

-10+10-10*10100 % = -1%

 Decrease in revenue = 1%

729 = 9 x 9 x 9

=> Cube root of 729 = 9

Now, required square of 9 = 9 x 9 = 81.

Total number of letters in the word ABYSMAL are 7

Number of ways these 7 letters can be arranged are 7! ways

But the letter is repeated and this can be arranged in 2! ways

Total number of ways arranging ABYSMAL = 7!/2! = 5040/2 = 2520 ways.

Let Althaf lent Rs. A at 14% per year.
Hence, Money lent at 12% = (1500-A);
Given, total interest = Rs. 186.
{(A x 14x 1)/100} + {[(1500-A) x 12 x 1/100]} = 186;
14A/100 + (18000 -12A)/100 = 186;
14A + 18000 - 12A = 186x100;
2A = 18600-18000;
A = 600/2 = Rs. 300.
Hence, money lent at 12% = 1500-300 = Rs. 1200.

In two throws of a die, n(s)=(6 x 6)=36

let E= Event of geting a sum 9={(3,6),(4,5),(5,4),(6,3)}

P(E) = n(E)/n(S) = 4/36 = 1/9

Let S be the sample space.
Here n(S)= 23 = 8
Let E be the event of getting atmost two heads. Then,
n(E) = {(H,T,T), (T,H,T), (T,T,H), (H,H,T), (T,H,H), (H,T,H)}
Required probability = n(E)/n(S) = 6/8 = 3/4.