SSC CGL 20201)The average age of A, B, and C is 20 years, and that of B and C is 25 years. What is the age of A ?
10 years
Average age of A, B and C = 20 years Total age of A, B and C = 60 years
Average age of B and C = 25 years total age of B and C = 50 years
A's age = 60 - 50 = 10 years
SSC CGL 20202)The average of four terms is 30 and the Ist term is \(\frac{1}{3}rd\) of the sum of the remaining terms. What is the first term?
30
Average of 4 numbers = 30; Sum of these numbers = 30 x 4 = 120; let Ist number is x.
so x = \(\frac{1}{3}(120-x)\); x = 30
SSC CGL 20203)In a class, the average score of thirty students on a test is 69. Later on it was found that the score of one student was wrongly read as 88 instead of 58. The actual average score is:
68
When data read wrongly then total score of thirty students on a test = 69 X 30 = 2070; (Average = sum of all terms/number of terms)
Difference in data = 88 - 58 = 30;
Actual score = 2070 - 30 = 2040;
Actual average score = 2040/30 = 68
SSC CGL 20204)The average score in Mathematics of 90 students of sections A and B together is 49. The number of students in A was 25% more than that of B, and the average score of the students in B was 20% higher than that of the students in A. What is the average score of the students in section A?
45
Let no. of students in section B = x ; A = 1.25x; then x + 1.25x = 90; therefore' x = 40;
Let average of score of section A be y and B be 1.2y;
then 50y + (1.2y x 40) = 90 x 49; y = 45
SSC CGL 20205)The average of five consecutive odd numbers is m. If the next three odd numbers are also included, then what is the increase in the average ?
3
Let five odd numbers be (x - 4), (x - 2), x, (x + 2), (x + 4) ; Average = \((x - 4)+ (x - 2)+ x+ (x + 2)+ (x + 4)\over5\) = m; x = m; Therefore, Sum of 5 number = 5m; New average = (Sum of 5 number + Sum of 3 number) / 8; ⇒ \({5m+m+6+m+8+m+10\over8} ={8m+24\over8}=m+3\);
SSC CGL 20206)The average of 60 student’s results is 38. If the average of the first 22 students is 36, and that of the last 32 students is 32, then the average result of the remaining students is:
77.33
Average of results of 60 students = 38; Total of results of 60 students = 60 x 38 = 2280; Average of results of 22 students = 36; Total of results of 22 students = 36 x 22 = 792; Average of results of 32 students = 32; Total of results of 32 students = 32 x 32 = 1024; Sum of results of the remaining 6 students = 2280 - 792 - 1024 = 464; Required average = \({464\over6} = 77.33\)
SSC CGL 20207)24 students collected money for donation. The average contribution was Rs. 50. Later on, their teacher also contributed some money. Now the average contribution is Rs. 56. The teacher’s contribution is:
Rs. 200
Total money contribution by 24 students = Average x No. of students = 50 x 24 = 1200; Total money contribution by 24 students and their teacher = 56 x 25 = 1400 ; Teacher’s contribution = 1400 - 1200 = Rs.200
SSC CGL 20208)The average of the marks of 30 boys is 88, and when the top two scores were excluded, the average marks reduced to 87.5. If the top two scores differ by 2, then the highest mark is:
96
Average marks of 30 students = 88; Let top two marks be x and x + 2. According to the question, \(30\times88-x-(x+2)=28\times87.5\); x= 94; So highest marks = x + 2 = 94 + 2 = 96
SSC CGL 20209)The average height of 5 boys is 175 cm. A sixth boy joined the group and the average height of all the boys in the group now increased by 1 cm. The height of the sixth boy is:
181 cm
Height of sixth boy = 175 cm + total increase = (175 + 1 x 6) = 181 cm
SSC CGL 202010)The average of some numbers is 54.6. If 75% of the numbers are increased by 5.6 each, and the rest are decreased by 8.4 each, then what is the average of the numbers so obtained?
56.7
New average of the numbers = (average + increment/decrements);
The average of some numbers = 54.6;
75% of the numbers are increased by 5.6 each, and the rest are decreased by 8.4 each so,
New average of the numbers = \(54.6 +\) \((5.6 \times 75/100 - 8.4 \times 25/100)\) = 54.6 + 4.2 - 2.1 = 56.7