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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}

Similar Questions :

1. 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

2. 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

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

  • 55
  • 56
  • 57
  • 58

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. The average of four consecutive odd numbers is 24. Find the largest number.

  • 25
  • 27
  • 29
  • 31

Answer: Option B

Explanation:

Let the numbers are x, x+2, x+4, x+6, then
\begin{aligned}
=> \frac{x+(x+2)+(x+4)+(x+6)}{4} = 24
\end{aligned}

\begin{aligned}
=> \frac{4x+12)}{4} = 24
\end{aligned}

\begin{aligned}
=> x+3 = 24 => x = 21
\end{aligned}

So largest number is 21 + 6 = 27

5. 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

  • 36
  • 37
  • 38
  • 39

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

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