15. The average of five consecutive odd numbers is 61. What is the difference between the highest and lowest numbers?
A.2
B.5
C.8
D.Cannot be determined

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16. The sum of three consecutive odd numbers is 38 more than the average of these numbers. What is the first of these numbers?
A.13
B.17
C.19
D.Data inadequate

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17. The average age of the boys in a class is 16 years and that of the girls is 15 years. The average age for the whole class is :
A.15 years
B.15.5 years
C.16 years
D.Cannot be computed with the given information

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18. A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is :
A.250
B.276
C.280
D.285

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19. If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55 and 60, then the average marks of all the students is :
A.53.33
B.54.68
C.55
D.None of these

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20. The average weight of 16 boys in a class is 50.25 kgs and that of the remaining 8 boys is 45.15 kgs. Find the average weight of all the boys in the class
A.47.55 kgs
B.48 kgs
C.48.55 kgs
D.49.25 kgs

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21. A car owner buys petrol at Rs 7.50, Rs. 8 and Rs. 8.50 per litre for three successive years. What approximately is the average cost per litre of petrol if he spends Rs. 4000 each year ?
A.Rs.7.98
B.Rs.8
C.Rs.8.50
D.Rs.9

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