Question

Find the range 19. (i) Find the class mark of the class 90-120. (ü) In a frequency distribution, the mid-value of the class is 10 and width of the class is 6. Find the lower limit of the class. (ii) The width of each of five continuous classes in a frequency distribution is 5 and lower class limit of the lowest class is 10. What is the upper class limit of the highest class? (iv) The class marks of a frequency distribution are 15, 20, 25, .... Find the class corresponding to the class mark 20. (v) In the class intervals 10–20, 20–30, find the class in which 20 is included.​

Answer 1

Step-by-step explanation:

(i) class mark =upper limit+lower limit/2=120+90/2=105

(ii) mid-value = 10

width = 6

Let the lower limit of the class be x.

upper limit = x + 6

class mark/mid - value =upper limit+lower limit/2

x+ (x+6 )/2=10

⇒ x = 7

(iii) width = 5

lower class limit of lowest class = 10

The classes will be 10-15, 15-20, 20-25, 25-30, 30-35.

Upper class limit of the highest class = 35.

(iv) Class marks = 15, 20, 25, ...class size = 20 - 15 = 5

Let lower limit of class be x.

x+ (x+5 )/2=20

⇒ x = 17. 5

Thus, the class is 17.5-22.5.

(v) 20 will be included in the class interval 20-30.