Quantitative Aptitude - Arithmetic Ability Questions

Let Rajeev's present age be  x years.

Rajeev's age after 15 years = (x + 15) years.

Rajeev's age 5 years back = (x - 5) years

Then ATQ, 

x + 15 = 5 (x - 5)

x + 15 = 5x - 25

=> x = 10

Hence, Rajeev's present age = x = 10 years.

Here a = 3 and r = 6/3 = 2. Let the number of terms be n.
Then, t = 384 => a * r^(n-1) = 384
=> 3 * 2^(n-1) = 384 => 2^(n-1) = 128 = 2^(7)

=> n-1 = 7 => n = 8.

Clearly, we have (3 + 11 + 7 + 9 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + x) / 12 = 12.

or  137 + x = 144 or x = 144 - 137 = 7.

125 over 1000 in Simplest Form means 1251000 in its simple fraction form.

Now, to get the simplest form of 125/1000, find the HCF or GCD of both numerator and denominator i.e, 125 and 1000.

HCF of 125, 1000 = 125

Then, divide both numerator and denominator by 125

i.e, 1251251000125 = 18

Hence, 18 is the simplest form of 125 over 1000.

Total age of 10 students = 150 years

Total age of 15 students = 240 years

Total age of 5 new students = 240 - 150 = 90 years

 Average age of 5 new students =  = 18 years

Required Number = (L.C.M  of 12, 16, 18,21,28)+7

= 1008 + 7

= 1015

Given M.P=45,S.P=42, Profit = 0.05

Let C.P=x , Then

Profit = (42-x)/x = 0.05
=> x = 40.