Quantitative Aptitude - Arithmetic Ability Questions

Given R + S + M + D = 76

=> R+7 : S+7 : M+7 : D+7 = 7:6:5:8

=> Let the ratio = x

=> M+7 = 5x

=> M = 5x-7

=> R = 7x-7

=> S = 6x-7

=> D = 8x-7

=> R + S + M + D = 76

=> 7x-7 + 6x-7 + 5x-7 + 8x-7 = 76

=> 26x - 28 = 76

=> 26x = 104

=> x = 4

=> Mahesh's present age = 5x-7 = 20 - 7 = 13 years.

The number of arrangements of 4 different digits taken 4 at a time is given by 4P4 = 4! = 24.All the four digits will occur equal number of times at each of the position,namely ones,tens,hundreds,thousands.

Thus,each digit will occur 24/4 = 6 times in each of the position.The sum of digits in one's position will be 6 x (1+3+5+7) = 96.Similar is the case in ten's,hundred's and thousand's places.

Therefore,the sum will be 96 + 96 x 10 + 96 x 100 + 96 x 100 = 106656

Let the edge of the cube be a.  

 so, the diagonal  a3 = 63    

=> a=6 

 Surface area = 6a2 = 6 x 6 x 6 = 216 sq.cm

Let the C.P of one item is Rs. P
and that of other is Rs. (7500 - P)

According to the data given
C.P = S.P
=> Px(116/100) + (7500-P)x(86/100) = 7500
=> 30P = 105000
=> P = 3500

Required difference between selling prices
= Rs. [(3500/100) x 116] - [(4000/100) x 86]
= 4060-3440
= Rs. 620

we can do this by trial and error method.

Putting x = 2,we get 2²(2² - 1) = 12.
checking with other integers, the above equation always gives a value which is a multiple of 12,
So, x²(x² - 1) is always divisible by 12.

Suppose age of each women be W and average age of 12 men be x

Hence , each woman's age = 24 years

          2000xX100 + 4000xY100 = 320

and     2000xX100 + 10000xY100 = 680

x = 4  and  y = 6

x-y = -2