Question
Calculate the mean of the distribution given below using the short cut method.
 
Marks 11 - 20 21 - 30 31 - 40 41 - 50 51 - 60 61 - 70 71 - 80
No. of students 2 6 10 12 9 7 4

Answer

Marks f x d=X-A=X

-45.5
fd
11-20 2 15.5 -30 -60
21-30 6 25.5 -20 -120
31-40 10 35..5 -10 -100
41-50 12 A=45.5 0 0
51-60 9 55.5 10 90
61-70 7 65.5 20 140
71-80 4 75.5 30 120
  $\Sigma$ f=50     $\Sigma$ fd=70
$\therefore \text { Mean }= A +\frac{\sum f d}{\sum f}$
$=45.5+\frac{70}{50}$
$=45.5+\frac{7}{5}$
$=\frac{227.5+7}{5}$
$=\frac{234.5}{5}$
$=46.9$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

If $4 \cos2 A – 3 = 0$, Show that:
$\cos 3 A = 4 \cos^3 A – 3 \cos A$
In the given figure, AE is the diameter of the circle. Write down the numerical value of ∠ABC + ∠CDE. Give reasons for your answer.
In what ratio does the point $(1, a)$ divided the join of $(-1, 4)$ and $( 4, -1)?$ Also, find the value of a.
Prove that any four vertices of a regular pentagon are concylic (lie on the same circle)
Estimate the median, the lower quartile and the upper quartile of the following frequency distribution by drawing an ogive: 
Marks(more than) 90 80 70 60 50 40 30 20 10 0
No. of students 6 13 22 34 48 60 70 78 80 80
The following table gives the wages (in ₹) of workers (per day) in a factory:
Wages (₹/day)130 -134134 - 138138 - 142142 - 146146 - 150
No. of workers58141211
There is a square field whose side is $44\ m.$ A square flower bed is prepared in its centre leaving a gravel path all round the flower bed. The total cost of laying the flower bed and graving the path at $Rs\ 2. 75$ and $Rs. 1.5$ per square metre, respectively, is $Rs. 4,904.$ Find the width of the gravel path.
If the midpoints of the sides ofa triangle are $(-2, 3), (4, -3), (4, 5),$ find its vertices. 
Find the coordinate of $O$, the centre of a circle passing through $P(3,0), Q(2, \sqrt{5})$ and $R(-2 \sqrt{2}$ $,-1)$. Also find its radius.
Given $A=\left[\begin{array}{cc}2 & 0 \\ -1 & 7\end{array}\right]$ and $1=\left[\begin{array}{ll}1 & 0 \\ 0 & 1\end{array}\right]$ and $A^2=9 A+m l$. Find $m$