The sum of two numbers is 126 and their diff is 18. Find the numbers.


Ans:
        x+y=126
        x-y=18
       
      so, 2x=144 and x=72
      so, 72+y=126
      y=126-72=54


so, the two numbers are 72 and 54. 

Pipe A & B can fill a tank in 20 hours, 30 hours respectively. And pipe C can empty the tank in 40 hours. If all pipes are opened together, how much time will be needed to make tank full?

Ans:
      = 1/20+1/30-1/40
      = 7/120
   
      = 120/7
      = 17 1/7
     

A,B,C partners invest 1600, 1800, 2300. Divide profit of 399Rs.

Ans:
      16+18+23=57
      16/57*399= Ans.
      18/57*399= Ans.
      23/57*399= Ans.

IIf asked.."In How Many Ways.."

(n-1)!=permutation
Suppose, in how many ways, 8 persons can be seated in a round table conference?


Ans:
       (n-1)! = 7!= 5040 Ans

See Short Cut Method

8 1/3 % of ? = 150

 25/3 * ? = 150

 ?= 150*3/25
   =18

X,Y,Z share money in ratio of 7:8:16. If Z receives Rs. 27 more than X, then find the total money.

Ans:
      7x, 8x, 16x
      16x= 7x + 27
       9x=27
         x=3
    
     7x+8x+16x = 31x=31*3= 93 Rs.

Money deposited by P,Q,R in ratio of 3:5:7. Q's share is 1500. What is the difference between p and Q's share?

Ans: 3x,5x,7x
    Q=5x=1500
           x=300

    P=900
    R=2100
   
    Diff=2100-900=1200