Mathmetics

ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams

Q531.
In a stream that is running at 2 km/hr , a man goes 10 km upstream and comes back to the starting point in 55 min. Find the speed of the man in still water  ?
1) 20 km/hr 2) 22 km/hr
3) 24 km/hr 4) 28 km/hr
5)None of these
Answer : 22 km/hr
Explanation :
Let the speed of the man in still water be x km/hr. then,
 km/hr.
        10/(x-2) + 10/(x+2) = 55/60
        or  x = 22 km/hr
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Q532.
The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:
1) 17 kg 2) 20 kg
3) 26 kg 4) 31 kg
5)None of these
Answer : 31 kg
Explanation :
Let A, B, C represent their respective weights. Then, we have:
A + B + C = (45 x 3) = 135 .... (i)
A + B = (40 x 2) = 80 .... (ii)
B + C = (43 x 2) = 86 ....(iii)
Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv)
Subtracting (i) from (iv), we get : B = 31.
B's weight = 31 kg.
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Q533.
The average monthly income of P and Q is Rs. 5050. The average monthly income of Q and R is Rs. 6250 and the average monthly income of P and R is Rs. 5200. The monthly income of P is:
1) 3500 2) 4000
3) 4050 4) 5000
5)None of these
Answer : 4000
Explanation :
Let P, Q and R represent their respective monthly incomes. Then, we have:
P + Q = (5050 x 2) = 10100 .... (i)
Q + R = (6250 x 2) = 12500 .... (ii)
P + R = (5200 x 2) = 10400 .... (iii)
Adding (i), (ii) and (iii), we get:  2(P + Q + R) = 33000  or   P + Q + R = 16500 .... (iv)
Subtracting (ii) from (iv), we get P = 4000.
P's monthly income = Rs. 4000.
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Q534.
The average monthly income of P and Q is Rs. 5050. The average monthly income of Q and R is Rs. 6250 and the average monthly income of P and R is Rs. 5200. The monthly income of P is:
1) 3500 2) 4000
3) 4050 4) 5000
5)None of these
Answer : 4000
Explanation :
Let P, Q and R represent their respective monthly incomes. Then, we have:
P + Q = (5050 x 2) = 10100 .... (i)
Q + R = (6250 x 2) = 12500 .... (ii)
P + R = (5200 x 2) = 10400 .... (iii)
Adding (i), (ii) and (iii), we get:  2(P + Q + R) = 33000  or   P + Q + R = 16500 .... (iv)
Subtracting (ii) from (iv), we get P = 4000.
P's monthly income = Rs. 4000.
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Q535.
The captain of a cricket team of 11 members is 26 years old and the wicket keeper is 3 years older. If the ages of these two are excluded, the average age of the remaining players is one year less than the average age of the whole team. What is the average age of the team ?

1) 23 years 2) 24 years
3) 25 years 4) 30 years
5)None of these
Answer : 23 years
Explanation :
        Let the average age of the whole team by x years.
Then,11x - (26 + 29) = 9(x -1)
or 11x - 9x = 46
or 2x = 46
or x = 23.
So, average age of the team is 23 years.

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Q536.
The average weight of 8 person's increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What might be the weight of the new person ?
1) 76 kg 2) 76.5 kg
3) 85 kg 4) Data Inadequate
5)None of these
Answer : 85 kg
Explanation :
Total weight increased = (8 x 2.5) kg = 20 kg.
So,weight of new person = (65 + 20) kg = 85 kg.
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Q537.
The average age of husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. The present age of the husband is:
1) 35 years 2) 40 years
3) 50 years 4) Data Inadequate
5)None of these
Answer : 40 years
Explanation :
Sum of the present ages of husband, wife and child = (27 x 3 + 3 x 3) years = 90 years.
Sum of the present ages of wife and child = (20 x 2 + 5 x 2) years = 50 years.
Husband's present age = (90 - 50) years = 40 years.
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Q538.
A batsman has a certain average of runs for 12 innings. In the 13th innings he scores 96 runs, there by  increasing his average  by 5 runs. What is his average after 13th innings ?
1) 34 2) 31
3) 36 4) 32
5)None of these
Answer : 36
Explanation :
Let the batsman’s average runs up to 12th innings was x.
Total run = 12 x.
Now total run up to 13th innings = (12 x + 96)
        According to equation = (12 x + 96)/13 = x + 5  or x = 31. 
So, after 13th innings average will be 31 + 5 = 36.

Shortcut Method :
96 - (135) + 5 = 36 
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Q539.
The average salary of workers of a Factory  is Rs.6000. While the average salary of 150 technician is Rs.12000 and that of the non-technician is Rs. 3750/-. Find the total member of the Factory. 
 
1) 500 2) 600
3) 550 4) 480
5)None of these
Answer : 550
Explanation :
By alligantion method :
12000 3750

  6000
6000 - 3750 = 2250 12000 - 6000 = 6000
So, final ratio = 2250 : 6000 = 3 : 8 
So,total number of employees = (150/3) x 11 = 550
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Q540.
The average mark of 48 students in a class is 45. The average marks of the boys in the class is 40 & the average mark of the girls in the class is 50. What is the ratio between the number of boys and  girls in the class ?      
1) 3:5 2) 1:1
3) 4:5 4) D.I
5)None of these
Answer : 1:1
Explanation :
With the help of alligation method :
50      40 
  
     45  
45 - 40 = 5 50 - 45 = 5
So, final ratio = 5 : 5 = 1 : 1
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