Question

Calculate mean from following information by short-cut method.
Marks 0-10 10-20 20-30 30-40 40-50
No. of 4 6 10 20 10 Ans. X=30.2
Students​

Answer 1

I don't know what you mean by 'shortcut method', so i will solve he way i was taught.

Mean = Σfx / Σf

Here Σ means "summation" or "sum" of values.

First we can make a table of x, f and fx.

x would be the middle value of the marks' ranges, such as from 20-30, x would be 25. f means frequency, which means how many students scored with in a certain range, so from 0-10, 4 students scored as your question states.

x f f * x or fx

05 04 5 * 4 = 20

15 06 15 * 6 = 90

25 10 250

35 20 700

45 10 450

Σf would be the sum of all the values in the column of 'f', and Σfx would be the sum of all values in the column of 'fx'.

Σfx = 1510

Σf = 50

Mean = Σfx / Σf = 1510 / 50 = 30.2 (Ans)