1.Find the average of first 10 multiples of 7
A.35.5
B.37.5
C.38.5
D.40.5
sol:
(firstdigit+lastdigit)/2=7+70=77/2=38.5
2.The average weight of a class of 24 students is 35 kg. If the weight of the teacher be included, the average rises by 400 g. The weight of the teacher is
A.45
B.50
C.55
D.60
sol:each student weight is 30 kg
as teacher is included weight increased by 35.4
so teachers contribution is 35.4+24x0.4=45
3.When a student weighing 45 kgs left a class, the average weight of the remaining 59 students increased by 200g. What is the average weight of the remaining 59 students
A.55B.56C.57D.58
sol:Let the average weight of the 59 students be A.
So the total weight of the 59 of them will be 59*A.
The questions states that when the weight of this student who left is added, the total weight of the class = 59A + 45
When this student is also included, the average weight decreases by 0.2 kgs
=> 59A + 45 = 60A - 12
=> 45 + 12 = 60A - 59A
=> A = 57
So the total weight of the 59 of them will be 59*A.
The questions states that when the weight of this student who left is added, the total weight of the class = 59A + 45
When this student is also included, the average weight decreases by 0.2 kgs
=> 45 + 12 = 60A - 59A
=> A = 57
4.The average weight of three men A,B,C is 84kg.Another man D Joins the group and the average now becomes 80kg.If another man E whose weight is 3kg more than that of D replaces A,then The average weight of B,C D and E becomes 79kg.The weight of A is.
A.70kg
B.72kg
C.75kg
D.80kg
sol:
intially A,B,C, average weight is 84 so each weight is 84
another man D joins so average becomes 80 this is contributed to D=80-12=68
E weight is 3 more than that of D= 71
E replaces A so A=71+4=75
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