Aptitude - Average
11.
The average age of three boys is 16 years. If their ages are in the ratio 4 : 5 : 7, then the age of the youngest boy is :
Answer
Sum of the ages of 3 boys = (16 x 3) years = 48 years.
Sum of the ratio = 4 + 5 + 7 = 16
Age of the youngest = 48 x 4 16 years = 12 years.
Answer :
Option CExplanation :
Sum of the ages of 3 boys = (16 x 3) years = 48 years.
Sum of the ratio = 4 + 5 + 7 = 16
Age of the youngest = 48 x 4 16 years = 12 years.
12.
Average weight of 8 men is increased by 1.5 kg when one of the men who weighs 65 kg is replaced by a new man. The weight of the new man is :
Answer
Increased weight = (1.5 x 8)kg = 12 kg.
Weight of the new man = (65 + 12)kg = 77 kg
Answer :
Option DExplanation :
Increased weight = (1.5 x 8)kg = 12 kg.
Weight of the new man = (65 + 12)kg = 77 kg
13.
a, b, c, d, e are five consecutive odd numbers. Their average is
Answer
Average = a + (a + 2) + (a + 4) + (a + 6) + (a + 8) 5
= 5(a + 4) 5 = (a + 4)
Answer :
Option DExplanation :
Average = a + (a + 2) + (a + 4) + (a + 6) + (a + 8) 5
= 5(a + 4) 5 = (a + 4)
14.
The average age of 24 boys and their teachers is 15 years. When the teacher's age is excluded, the average age decreases by 1 year. The age of the teacher is
Answer
Sum of the ages of 24 boys and 1 teacher = (15 x 25) years = 375 years.
Sum of the ages of 24 boys = (24 x 14) years = 336 years.
Age of the teacher = (375 − 336) years = 39 years.
Answer :
Option BExplanation :
Sum of the ages of 24 boys and 1 teacher = (15 x 25) years = 375 years.
Sum of the ages of 24 boys = (24 x 14) years = 336 years.
Age of the teacher = (375 − 336) years = 39 years.
15.
The average of x1, x2, x3, x4 is 16. Half the sum of x2, x3, x4 is 23. What is the value of x1 ?
Answer
x1 + x2 + x3 + x4 4 = 16 ⇒ (x1 + x2 + x3 + x4) = 64
1 2 (x2 + x3 + x4) = 23 ⇒ (x2 + x3 + x4) = 46
∴ x1 = (64 − 46) = 18
Answer :
Option BExplanation :
x1 + x2 + x3 + x4 4 = 16 ⇒ (x1 + x2 + x3 + x4) = 64
1 2 (x2 + x3 + x4) = 23 ⇒ (x2 + x3 + x4) = 46
∴ x1 = (64 − 46) = 18
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