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- Question
Three maths classes: A, B and C take an algebra test. The average score of class A is 83. The average score of class B is 76. The average score of class C is 85. The average score of class A and B is 79 and average score of class B and C is 81. What is the average score of classes A, B, C ?
Options- A. 81
- B. 78
- C. 80.5
- D. 81.5
- Correct Answer
- 81.5
ExplanationLet the number of students in classes A, B and C be P, Q and R respectively.
Then, total score of A = 83P, total score of B = 76Q, total score of C = 85R.
Also given that,
(83P + 76Q) / (P + Q) = 79
=>4P = 3Q.
(76Q + 85R)/(Q + R) = 81
=>4R = 5Q,
=>Q = 4P/3 and R = 5P/3
Therefore, average score of A, B, C = ( 83P + 76Q + 85R ) / (P + Q + R) = 978/12 = 81.5 - 1. It costs Rs. p each to send the first thousand messsages and Rs. q to send each subsequent one . If r is greater than 1,000, how many Rupees will it cost to send r messages ?
Options- A. 1000 (r - p) + pq
- B. 1000 p + qr
- C. 1000 (r - q) + pr
- D. 1000(p - q) + qr Discuss
- 2. What will be the cost of building a fence around a square plot with area equal to 289 sq ft, if the price per foot of building the fence is Rs. 58 ?
Options- A. Rs. 3748
- B. Rs. 3847
- C. Rs. 3944
- D. Rs. 3154 Discuss
- 3. In a mixture of three varities of oils , the ratio of their weight is 4 : 5 : 8. If 5 kg of oils of the first variety, 10 kg of the second variety and some quantity of oils of the third variety are added to the mixture, the ratio of the weights of three varieties of oils becomes as 5 : 7 : 9 in the final mixture, find the quantity of third variety of oil was ?
Options- A. 15 kg
- B. 25 kg
- C. 35 kg
- D. 45 kg Discuss
- 4. After replacing an old member by a new member, it was found that the average age of five members of a club is the same as it was 3 years ago. The difference between the ages of the replaced and the new members?
Options- A. 16 years
- B. 15 years
- C. 14 years
- D. 13 years Discuss
- 5. 123 typists typeed 984 papers in 1/15 hour. The number of papers typed for minute by a average typist is:
Options- A. 1
- B. 2
- C. 3
- D. 5 Discuss
- 6. The average of marks in 3 subjects is 224. The first subject marks is twice the second and the second subject marks is twice the third. Find the second subject marks ?
Options- A. 384
- B. 96
- C. 192
- D. 206 Discuss
- 7. How many window coverings are necessary to span 50 windows, if each window covering is 15 windows long?
Options- A. 4
- B. 15
- C. 3
- D. 50 Discuss
- 8. 16 children are to be divided into two groups A and B of 10 and 6 children. The average percent marks obtained by the children of group A is 75 and the average percent marks of all the 16 children is 76. What is the average percent marks of children of group B ?
Options- A. 233/3
- B. 243/4
- C. 254/5
- D. 345/7 Discuss
- 9. 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 :
Options- A. 15
- B. 20
- C. 21
- D. data inadequate Discuss
- 10. What is the average of four tenths and five thousandths
Options- A. 25002
- B. 2502
- C. 0.2025
- D. none Discuss
Average problems
Search Results
Correct Answer: 1000(p - q) + qr
Explanation:
We need to find the total cost to send r messsages, r > 1000.
The first 1000 messsages will cost Rs.p each (Or)
The total cost of first 1000 messsages = Rs.1000p
The remaining (r - 1000) messsages will cost Rs.q each (Or)
The cost of the (r - 1000) = Rs.(r - 1000)y
Therefore, total cost = 1000p + rq - 1000q
= 1000(p - q) + qr
Correct Answer: Rs. 3944
Explanation:
Let the side of the square plot be 'a' ft.
Given area of the plot (a x a) = 289 => a = 17
Length of the fence = Perimeter of the plot = 4a = 68 ft.
Cost of building the fence = 68 x 58 = Rs. 3944.
Correct Answer: 45 kg
Explanation:
Let the ratio of initial quantity of oils be 'x' => 4x, 5x & 8x.
Let k be the quantity of third variety of oil in the final mixture.
Let the ratio of initial quantity of oils be 'y'
From given details,
4x + 5 = 5y ..... (1)
5x + 10 = 7y .....(2)
8x + k = 9y ......(3)
By solving (1) & (2), we get
x = 5 & y = 5
From (3) => k = 5
Therefore, quantity of third variety of oil was 9y = 9(5) = 45kg.
Correct Answer: 15 years
Explanation:
Let avg ages of 5 members at present is G
And age of new member is m and an older is n
Required = (5G + m - n)/5 = G - 3
m - n = 15 years
Correct Answer: 2
Correct Answer: 192
Explanation:
Let the third subject marks be 'x'
=> Second subject marks = 2x
=> Third subject marks = 4x
Given avg = 224
x + 2x + 4x = 224 x 3
=> 7x = 224 x 3
=> x = 96
Hence, Second subject marks = 2x = 2 x 96 = 192.
Correct Answer: 4
Explanation:
Given that,
Number of windows = 50
Each window covering covers 15 windows
=> 50 windows requires 50/15 window coverings
= 50/15 = 3.333
Hence, more than 3 window coverings are required. In the options 4 is more than 3.
Hence, 4 window coverings are required to cover 50 windows of each covering covers 15 windows.
Correct Answer: 233/3
Explanation:
Required average = [(76 * 16) - (75 * 10)] / 6 = (1216 - 750)/6 = 466/3 = 233 /3.
Correct Answer: data inadequate
Explanation:
Clearly, to find the average, we ought to know the number of boys, girls or students in the class, neither of which has been given.
So, the data provided is inadequate.
Correct Answer: 0.2025
Explanation:
Four tenths = 0.4
Five thousandths = 0.005
The average is (0.4 + 0.005)/2 = 0.2025
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