Question Detail

Average age of boys in a class is 16 years and average age of girls is 15 years, what is the average age of all

15.5
15
16
Cant be computed

Answer: Option D

Explanation:

As number of girls and boys is not given so result cant be computed

1. The average of six numbers is X and the average of three of these is Y.If the average of the remaining three is z, then

x = y + z
2x = y + z
x = 2y + z
x = y + 2z

Answer: Option B

Explanation:

X =((3y+3z)/6)
or
2X= y + z

2. Find the sum of first 30 natural numbers

Answer: Option C

Explanation:

Sum of n natural numbers

$\begin{aligned} = \frac{n(n+1)}{2} \end{aligned}$

$\begin{aligned} = \frac{30(30+1)}{2} = \frac{30(31)}{2} = 465 \end{aligned}$

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

Answer: Option C

Explanation:

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

$\begin{aligned} \frac{59A + 45}{60} = A - 0.2 \end{aligned}$

=> 59A + 45 = 60A - 12
=> 45 + 12 = 60A - 59A
=> A = 57

4. A batsman makes a score of 87 runs in the 17th match and thus increases his average by 3. Find his average after 17th match

Answer: Option D

Explanation:

Let the average after 17th match is x
then the average before 17th match is x-3

so 16(x-3) + 87 = 17x
=> x = 87 - 48 = 39

5. Find the average of first 10 multiples of 7

35.5
37.5
38.5
40.5

Answer: Option C

Explanation:

$\begin{aligned} = \frac {7(1+2+3+...+10)}{10} \end{aligned}$

$\begin{aligned} = \frac {7(10(10+1))}{10 \times 2} \end{aligned}$

$\begin{aligned} = \frac {7(110)}{10 \times 2} = 38.5 \end{aligned}$

chandu 10 years ago

Average age of boys in a class is 16 years and average age of girls is 15 years, what is the average age of all
15.5
15
16
Cant be computed
in this question answer is wrong
the correct answer is 15.5
bocz we dont know the no of girsl and boys but we know average of boys and girls so just make out avg of their avg ,
16+15/2=15.5