Quants

What will come in place of (?) in the following series?

1. 6, 4, 5, 11, 39, 189, ?
   A) 1039
   B) 1127
   C) 1150
   D) 1129
   E) 1189

B) 1127
Explanation: 
6*1 – 2, 4*2 – 3, 5*3 – 4, 11*4 – 5, 39*5 – 6, 189*6 – 7

0, 6, 60, 210, 504, ?
A) 950
B) 840
C) 990
D) 1010
E) None of these

C) 990
Explanation: 
0^3 – 0, 2^3 – 2, 4^3 – 4, 6^3 – 6, 8^3 – 8, 10^3 – 10

120, 80, 48, 24, ? 
A) 8
B) 12
C) 10
D) 16
E) 2

A) 8
Explanation: 
11^2 – 1, 9^2 – 1, 7^2 – 1, 5^2 – 1, 3^2 – 1

7, 11, 25, 47, ?

A) 120
B) 78
C) 115
D) 97
E) 102

D) 97
Explanation: 
7, 7*2 – 3, 11*2 + 3, 25*2 – 3, 47*2 + 3

12, 17, 30, 51, 80, ? 
A) 122
B) 102
C) 115
D) 136
E) None of these

E) None of these
Explanation: 
17-12 = 5, 30-17 = 13, 51-30 = 21, 80-51 = 29
13-5 = 8, 21-13 = 8, 29-21 = 8
So next number is 80+29+8 = 117

A milk vendor purchased pure milk at Rs 40 per litre. He diluted the milk with water and sold at Rs 40 per litre and in this he gains 60% profit. In diluted milk what is the amount of pure milk taken? 

Explanation: 
Since the diluted milk is sold at same price at which pure milk was bought,
Profit% = [(difference in actual weight and given)/(given weight)] * 100
Let from 1000 ml, x ml of pure milk is taken
Then [(1000-x)/x] * 100 = 60

 625 ml

5 kgs of wheat costing Rs 15 per kg is mixed with 10 kgs of wheat costing Rs 12 per kg. The mixture is then sold at 20% profit. Find the selling price of the mixture in Rs/kg. 

Short Cut:   5*15+10*12=195

Now,195+195*20%=234 rs

We have Quantity 15 kg,So 234/15=15.60

An old advisor of a company was replaced by a young man. As a result, the average age of the board of ten advisors of the company was the same as it was 4 years ago. How much younger is the young man who replaced the old advisor? 

Explanation: 
The difference of 4 years has come in the age of each of 9 remaining advisors, and since the average is the same, there is the difference of (4*9) = 36 years in the age of old and the young man

A and B alone can complete a work in 40 and 60 days respectively. A works on the work for some days and then B joins him and together they complete the work in 10 days less than the number of days A takes alone to complete the work. After how many days did B joined A? 

Explanation: 
Let A works for x days, now B joins and together they complete work in 30 days, this means A and B have together worked for (30-x) days.
So (1/40) * x + (1/40 + 1/60) * (30-x) = 1
Solve, x = 15

A is one and a half times more efficient than B. A alone can do a work in 20 days. What portion of total work can both of them together complete in 10 days? 

Let efficiency of B is x, then of A is 1 + 1(1/2) = 5x/2
Ratio of efficiencies of A : B = 5x/2 : x= 5 : 2
So ratio of number of days of A : B = 2 : 5
A completes work in 20 days, so 2x = 20, x = 10
So B alone completes work in 5x days = 50 days
(A+B)’s 1 day’s work = 1/20 + 1/50 = 7/100
So in 10 days, pat of work completed is 10 * (7/100) = 7/10