Mathematics Mcqs

If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 60, then the average marks of all the students is__________?

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If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 60, then the average marks of all the students is__________?

A. 53.33
B. 54.68
C. 55
D. None of these
Required average = (55 x 50 + 60 x 55 + 45 x 60) / (55 + 60 + 45)
= (2750 + 3300 + 2700) /160
= 54.68 is correct Answer

The average of 18 observations was calculated and it was 124. Later on it was discovered that two observations 46 and 82 were incorrect. The correct values are 64 and 28. The correct average of 18 observations is___________?

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The average of 18 observations was calculated and it was 124. Later on it was discovered that two observations 46 and 82 were incorrect. The correct values are 64 and 28. The correct average of 18 observations is___________?

A. 123
B. 137
C. 121
D. 122
Sum of 18 observations = 18×124 =2232
Correct sum of 18 observations = 2232-46-82+64+28
= 2196
Therefore, Correct average =2196/18 = 122

A person travels from x to y at a speed of 40Km/h and returns by increasing his speed 50%. What is his average speed for both the trips?

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A person travels from x to y at a speed of 40Km/h and returns by increasing his speed 50%. What is his average speed for both the trips?

A. 36km/h
B. 45km/h
C. 48km/h
D. 50km/h
Explanation:
Speed of person from x to y =40 km/h
Speed of person from y to x =(40×150)/100 = 60km/h
Since the distance travelled is same
Therefore, Average Speed = (2x40x60)/40+60 = 48km/h

The average of women and child workers in a factory was 15%yr. The average age of all the 16 children was 8yr and average age of women workers was 22 yrs if ten women workers were married then the number of unmarried women workers were________?

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The average of women and child workers in a factory was 15%yr. The average age of all the 16 children was 8yr and average age of women workers was 22 yrs if ten women workers were married then the number of unmarried women workers were________?

A. 16
B. 12
C. 8
D. 6
Let the number of women workers be x
According to the question 22*x+16*8 = 15(16+x)
=> 22x+128 =240 +15x
=> 22x-15x = 240 -128
=> 7x=112
Therefore, x=112/7 =16
Therefore, Unmarried women workers =(16-10) = 6

The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years. The ration of the number of boys to the number of girls in the class is___________?

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The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years. The ration of the number of boys to the number of girls in the class is___________?

A. 1:2
B. 2:3
C. 3:4
D. 3:5
Let the ratio be k : 1. Then,
k * 16.4 + 1 * 15.4 = (k + 1) * 15.8
= (16.4 – 15.8)k = (15.8 – 15.4)
= k = 0.4/0.6 = 2/3
Required ratio = 2/3 : 1 = 2:3