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### Mathmetics

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

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##### The batting average of 30 innings of a cricketer is 40 runs. His highest score exceeds his lowest score by 100 runs.If these two innings are not included, the average of the remaining 28 innings is 38. What is the lowest score of the player ?
 1) 12 2) 16 3) 18 4) 20 5) None of these
Explanation : Let, the highest and lowest score  are x and y respectively.
So, x + y = (40 X 30 ) - (28 X 38) = 136  -------- (i)
Given, x-y = 100  -------- (ii)
Given, x-y = 100
By solving, the above equation  we get, x= 118 and x = 18 View Answer
##### The average salary of 16 employees in a company is Rs.800 per month. If the manager’s salary is added, the average salary increase by Rs.50. What is the salary of the manager ?
 1) Rs.1650 2) Rs.2000 3) Rs.2400 4) Rs.3500 5) None of these
Explanation :
Short-cut Method :
(Final Strength  X Increases Value) + earlier average
i.e. ( 17 X 50) + 800 = Rs. 1650 View Answer
##### The average age of 50 students of a class is 16 years. When 10 new students are admitted, then the average age increased by 0.5 years. What is the average age of the new students ?
 1) 17 years 2) 18 years 3) 19 years 4) 20 years 5) None of these
Answer : 19 years
Explanation : The total age of 50 students = 50 X 16 = 800 yrs.
After admitted 10 new students ,total age become 60 X 16.5 = 990 yrs.
So, age of new students = 990 -800 = 190 yrs.
Thus, their average 190 /10 = 19 yrs. View Answer
##### The average expenditure of a man for the first five month of a year is Rs.5,000 and for the next seven- month is Rs-5,400. He saves Rs.2,300 during the year. What his average monthly income ?
 1) Rs.5,425 2) Rs.5,500 3) Rs.5,446 4) Rs.5,600 5) None of these
Explanation :
Total expenditure is = (55000 + 75400) = 62800
His saving is Rs. 2300
Total annual income = 62800 + 2300 = 65100
Monthly income = 65100 ÷ 12 = Rs. 5425 View Answer
##### There are some adult students in a class and their average age was 40 years. If 12 new students with an average age of 50 years join with them, their new average age will be increases by 5 years.What was the original strength of that class ?
 1) 8 2) 10 3) 12 4) 15 5) None of these
Explanation : Let, there were x number of students in the class.
Given that their average age was 40 yrs.
So, their total age was = 40x yrs
Now, 12 new students join with them with an average age of 50 yrs.
Then, total age was = (12 x 50) = 600 yrs. and total students were x+12.
Now, new total age was = (4x + 600 ) yrs.
So, (40x + 600 ) / (x+12) = 45
or 45x + 540 = 40x + 600
or 5x = 600 -540 = 60
or x = 60/5 = 12
Thus, original strength of that class was 12. View Answer
##### The average age of a class of 30 students is 12. If the teacher is also included the average becomes 13 years. Find the teacher's age.
 1) 39 years 2) 40 years 3) 44 years 4) Data Inadequate 5) None of these
Answer : 39 years
Explanation :
When the teacher is included there are totally 31 members in the class and the average is increased by 1 year. This means that everyone got 1 extra year after distributing the extra years of the teacher.
So, extra years of the teacher are as follow: 31Ã—1=31 years.
Age of the teacher = actual avg + extra years = 12 + 31 = 43 years
Age of the teacher = (25 x 15 - 24 x 14) = 39 years. View Answer
##### There were 35 students in a hostel. If the number of the students is increased by 7, then the expenses of the mess increase by Rs.42 per day, while the average expenditure per head diminishes by Rs.1. What the original expenditure of the mess per day ?
 1) Rs.400 2) Rs.432 3) Rs.442 4) Rs.420 5) None of these
Explanation : Let, the average expenditure of the mess per day is Rs.x.
Then, total expenditure/day = Rs.35x
Now, total students = 35+7= 42 and new expenditure of the mess =  Rs.(35x +42)
So, Rs.(35x +42) /42 = Rs.x-1
or 35x + 42 = 42x -42
or 7x = 84
or x = 12
Therefore, original expenditure of the mess = 35 x 12= Rs.420 View Answer
##### In an examination, a student's average marks were 63. If he had obtained 20 more marks for his Mathematics and 2 more marks for his Geography, his average would have been 65. How many subjects were there in the examination ?
 1) 8 2) 10 3) 11 4) 14 5) None of these
Explanation :
Let, the number of subjects = x
Then, Total marks he scored for all subjects = 63x
If he had obtained 20 more marks for his mathematics and 2 more marks for his geography, his average would have been 65.
=> Total marks he would have scored for all subjects = 65x
Now, we can form the equation as 65x - 63x = the additional marks of the student
= 20 + 2 = 22
=> 2x = 22
=>x=22/2=11 View Answer
##### A batsman makes a score of 96 runs in the 16th innings and thus increases his averages by 2. What is his average runs after 16th innings ?
 1) 62 2) 64 3) 66 4) 72 5) None of these
Explanation :
Let, the average up to 15th innings = x.
Total runs scored in 15 innings = 15x
Then average after 16 innings = (x+2).
Total runs scored in 16 innings = (15x + 96)
So, (15x + 96)/16 = (x+2)
=> 15x + 96 = 16x + 32
=> x = 64
Therefore, his average run after 16th innings is 64+2= 66 runs. View Answer
##### The average weight of 10 person  increases by 3 kg when a new person comes in place of one of them weighing 45 kg. What is the weight of the new person?
 1) 75 Kg 2) 65 Kg 3) 80 Kg 4) 85 Kg 5) None of these
Answer : 75 Kg
Explanation :
Total increase in weight = 10×3 = 30
If x is the weight of the new person, total increase in weight = x - 45
=> 30 = x - 45
=> x = 30 + 45 = 75 kg View Answer

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