Question

1. A sum of rs.850 is divided into three parts, proportional to 1/3:2/5:3/7 find the value of the first part?
A. Rs.280.50
B. Rs.242.75
C. Rs.269
D. Rs. 243.85
2.if an amount gets doubles in 6years at simple intrest, then is how many years will it become 4 times?
A. 18 years
B. 12 years
C. 10 years
D. 15 years
3. What is the fourth proportional to 3,9,21,? Which number replaces the question mark?
A. 81
B. 27
C. 54
D. 63
4. A shopkeeper doubles the selling price as a result profit triples. What is the profit percentage of the shopkeeper?
A. 80%
B. 100%
C. 75%
D. 66%
5. A train wheel of diameter of 49cm travels a distance of 154km. How many numbers of revolutions does the wheel make?
A. 96
B. 108
C. 100
D. 120

Answer 1

1)  x: y: z = 1/3 : 2/5 : 3/7    = multiply by LCM of denominators
            = 35/105 : 42/105 : 45/105
   X gets 35/105 * 850

2) Sum becomes twice in 6 years in simple interest.
       Sum = 2 P = P + P (r/100) 6    =>      r 6/100 = 1     => r = 100/6 %
       Sum = 4 P = P + P * 100/(6*100)  t    =>  t = 3 * 6 = 18 years 

3) 3 : 9 :: 21 : 63   

4) SP = CP + CP * Profit%/100 = CP  (1+Profit%/100)
    SP' = 2 SP = 2 CP ( 1 + profit%/100) 
          = CP + 3 * CP * profit%/100
         =>  2 + 2 Profit%/100 = 1 + 3 Profit%/100
               Profit% = 100

5)  distance = Pi * diameter * n = 154 *1000*100 cm
                 n = 154 * 1000 * 100 / Pi / 49  = 100,000/7 revolutions