test 1

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1.The average marks obtained by 120 cndidates in a certain examinationis 35.if the average marks of passed candidate is 39 and that of the failed candidates is 15,what is the number of candidates who passed the examination?

110                       
100                       
120                       
115                       
None of these        


(b) Let No. of passed candidates are x 
 So, x * 39 + (120 – x) 15= 120 * 35 x = 100

2.The average age of 8 persons in a committee is increased by 2 years when two men aged 35 years and 45 years are substituted by two women.Find the average age of these two women.

48                          
36                         
42                         
29                         
None of these        
 (a) Total increase = 8 * 2 = 16 years So, 
  total age of two women = 35 + 45 +16= 96 
  Average age of two women=96/2=48 years

3.In a class, there are 20 boys whose average age is decreased by 2 months, when one boy aged 18 years is replaced by a new boy.Find the age of new boy.

19 years                 
14 years 6 month    
15 years                
14 years 8 month    
12 years                 


(d) Total decrease = 20 * 2 = 40 month = 3 years 4 month 
  So, age of new boy = 18 years – 3 years 4 month 
  = 14 years 8 month

4.One -third of certain journey is covered at the rate of 25kmph,one-fourth at the rate of 30kmph and the rest at 50 kmph.Find the average speed for the whole journey.

33.33 kmph             
36                           
42                           
27                           
none of these           


(a) Average speed = total distance / total time 
   LCM = 3, 4 = 12 
   Average speed = 12 / (1/3*12*1/25 + ¼ * 12*1/30 +5/50) 
   = 12/ (4/25 + 3/30+ 5/30 
   = 150*12/54 = 33.333 kmph

5.The average salary of the entire staff in a office is Rs 120 per month.The average salary of officers is Rs 460 and of non officers is Rs 110. If the number of officers is 15,then find the No of non-officers in the office.

480                         
500                         
600                        
430                         
510                         


(e) Let no. of non- officers be x 
 15 * 460 + x * 110 = (x + 15) 120 
  x = 510

6. There were 35 students in a hostel.If the number of students increased by 7, the expenses of the mess increases by Rs. 42 per day,while the average expenditure per head diminishes by Rs.1.Find the original expenditure of the mess.

420                      
400                     
480                     
460                     
None of these      


(a) Let average expenditure per head be = x 
 So, (35 + 7) (x -1) – 35 x = 42
 42 (x -1) – 35x = 42 
 X =12 
 Original expenditure of mess = 12 * 35 = 420

7.The average weight of A,B,and C is 84 kg. If D joins the group, the average weight of the group becomes 80 kg.If another man E who weights is 3 kg more than D Replaces A, Then the average of B,C,Dand E becomes 79 kg. What is the weight of A?

64                     
72                    
75                      
100                    
80                      


(c) A + B + C = 3 *84 = 252 A + B + C + D = 4 * 80 = 320 ---- (i)
 So, D = 68& E = 68 + 3 = 71 B + C + D +E = 79 * 4 = 316 --- (ii)
 From Eq. (i) & (ii) A-E = 320 – 316 = 4 A = E +4 = 71 + 4 = 75

8.In an exam, the average was found to be 50 marks. After deducting computational errors the marks of the 100 candidates had to be changed from 90 to 60 each and average came down to 45 marks. Total No of candidates who took the exam were.

300                     
600                      
200                      
150                      
None of these       


(b) Let the total no. of candidates = x 
 So, (50x-100 (90-60)) / x = 45
 x = 600

9.Find the average of all even No's up to 100 or average of first 50 even No's.

50                     
50.5                  
51                      
49                     
None of these    


(c) 2, 4, 6, ………… 100 
   Average = (1st No. + Last No.) /2 = (2+100)/2 = 51

10.The average of 8 No's is 20. The average of first two No's is 15.5 and that of next three No's is 64/3.if the 6th No be less than the seventh and eight No. by 4 and 7 respectively, then find eight No.

26                     
25.5                  
27                      
25                     
None of these    


(c) Total Sum of 8 nos. = 20 * 8 = 160
 Sum of 1st two nos. = 2 * 15.5 = 31 
 Sum of next three nos. = 3 * 64/3 = 64 
 Let 6th no. be x 31 + 64 + x + (x+4) + (x+7) = 160 
 x = 18 
 8th no. = 18 + 7 = 25

                                       

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