4.Mallapragada's. Mathematics /Average -(2)

Average -2

Sl.No.	Problems	Ans.
1	A family consists of grandparents, parents and three grandchildren. The average age of the grandparents is 70 years, that of the parents is 40 years and that of grandchildren is 10 years what is the average age of the family
2	The average marks of three batches of 55,60 and 50 Students respectively is 50,55,60 then the average marks of all the students is.
3	Out of 9 persons, 8 persons spent Rs 60 each for their meals. The ninth one spent Rs. 30 more than the average expenditure of all the nine. The total money spent by all of them was.
4	The average of six numbers is 3.50.  The average of two of the 2.5, while the average of the other two is 2.1What is the average of the remaining two numbers. ?
5	The average of five consecutive numbers is n. if the next two numbers are also included , the average will:
6	The average height of 2.1 m.  when 6 boys leave the group. Then the average height increases by 0.15m. what is the average height of the 5 boys who leave ?
7	A team of 8 persons joins in a shooting competition. The best marksman scord 80 points.  If he has scored 90 points. The average scoe for the team would have been 80. The number of points, the team scored was:
8	A motorist travels to a place 100km away at an average speed of 50km./ hr. and returns at 30km/hr his average speed for the whole journey in km/hr is:
9	Three years ago, the average age of A and B was 20 years With C joining them, the average age becomes 22 years.  How old is C now?
10	The average salary of all the workers in a workshop is Rs. 10,000.   The average salary of 8 technicians is Rs. 12,000 and the average salary of the rest is Rs. 6000. The total number of workers in the workshop is:
11	The average of runs of a cricket player of 10 innings was 36.  How many runs must he make in his next innings so as to increase his average of runs by 4 ?
12	In the first 10 overs  of a cricket game.  The run rate was only 4.2.  What should be the run rate in the remaining 40 overs to reach the target of 282 runs.?
13	The average price of three items of furniture is 20000. If their prices are in the ratio 3:5:7the price of the cheapest items is:
14	If the arithmetic mean of seventy five numbers is calculated, it is 35.  If each number is increased by 5, then mean of new numbers is:
15	The average age of 15 students of a class is 15 years.  Out of these, the average age of 5 students is 14 years and that of the other 9 students is 16 years.  The age of the 15 th student?
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Om Sri ram      Om Sri  Ram    Om Sri Ram

1	A family consists of grandparents, parents and three grandchildren. The average age of the grandparents is 70 years, that of the parents is 40 years and that of grandchildren is 10 years what is the average age of the family Ans. Required average     =250/7 = 35.71years.
2	The average marks of three batches of 55,60 and 50 Students respectively is 50,55,60 then the average marks of all the students is. Ans. 2750+3300+3000/165=         9050/165= 54.84
3	Out of 9 persons, 8 persons spent Rs 60 each for their meals. The ninth one spent Rs. 30 more than the average expenditure of all the nine. The total money spent by all of them was. Ans. 9x = 8 x 60 +(x+30) = 8x = 510 x=63.75          The total money spent 9 x 63.75=Rs.             573.75
4	The average of six numbers is 3.50.  The average of two of the  2.5, while the average of the other two is 2.1What is the average of the remaining two numbers. ? Ans. Sum of the remaining two numbers          3.50 x 6 (2.5 x 2 + 2.1 X 2 )=21-(5+4.2)=11.8          Required average 11.8/2 = 5.9
5	The average of five consecutive numbers is n. if the next two numbers are also included , the average will: Ans.  five consecutive numbers is n          x,x+1,x+2,x+3, and x+4, Their average is          =  = x + 2         Average numbers of seven is          =  = (7x + 21)/7 =x+3         So average increased by 1
6.	The average height of 25 boys is  2.1 m.  when 6 boys leave the group. Then the average height increases by 0.15m. what is the average height of the 5 boys who leave ? Ans. sum of height 6 boys= 25 x 2.1 – 19 x 1.5=          52.5 – 28.5 =24m
7.	A team of 8 persons joins in a shooting competition. The best marksman scored 81 points.  If he has scored 90 points. The average score for the team would have been 80. The number of points, the team scored was: Ans. Let the Total Score of x          80  = x +9 = 8 x 80          X= 631
8	A motorist travels to a place 100km away at an average speed of 50km./ hr. and returns at 30km/hr his average speed for the whole journey in km/hr is: Ans. Average speed=  km/hr. =3.75
9	Three years ago, the average age of A and B was 20 years With C joining them, the average age becomes 22 years.  How old is C now? Ans. Present age of A+B=20x2 + 3x 2= 46 A + B +C= 22x 3 =66 Therefore=66-46=20, c=20
10	The average salary of all the workers in a workshop is Rs. 10,000.   The average salary of 8 technicians is Rs. 12,000 and the average salary of the rest is Rs. 6000. The total number of workers in the workshop is:  Ans. Let the total numbers = x          10,000x = 8x12000-8 x 6000           X = (96000-48000)/10000= 48000/10000           X = 4.8
11	The average of runs of a cricket player of 10 innings was 36.  How many runs must he make in his next innings so as to increase his average of runs by 4 ? Ans. Average after 11 innings 40          Required number of runs  (11x40)-(10x36)           = 440 – 360 = 80
12	In the first 10 ovears  of a cricket game.  The run rate was only 4.2.  What should be the run rate in the remaining 40 overs to reach the target of 282 runs.? Ans. Required run rate is 282-(10 x 4.2)/40          282-42/40 = 240/40 = 6
13	The average price of three items of furniture is 150000. If their prices are in the ratio 3:5:7the price of the cheapest items is: Ans. Let their prices be 3x,5x,7x          Then (3x + 5x+7x)/3 = 15000         15x = 15000x3 = 3000          Cost of cheapest item = 3x = 3x3000=9000
14	If the arithmetic mean of seventy five numbers is calculated, it is 35.  If each number is increased by 5, then mean of new numbers is: Ans. A.M. of 75 numbers=35           Sum of 75 numbers= 75 x 35 =2625           Total increase = 75 x 5= 375.            Increased sum = 2625 + 375 = 3000            Increased average = 3000/75= 40
15	The average age of 15 students of a class is 15 years.  Out of these, the average age of 5 students is 14 years and that of the other 9 students is 16 years.  The age of the 15 th student? Ans. The age of 15 student =                                15 x15 –(5x14)+(9x16)= 225-214=11 years.