Question

Marks of 10 students are as follows: 25, 30, 15, 22, 20, 12, 26, 20, 25 and x. If the mean of the marks is 21, what will be the value of x?
a. 25

b. 20

c. 22

d. 15​

Answer 1

Answer:

(25+30+15+22+20+12+26+20+25+x)/10= 21

(195+x)=210

x=15

option (d) is answer

Answer 2

Answer:

25+30+15+22+20+12+26+20+25+x = 195+x

(195+x)/10 = 21

Cross Multiplication

195+x = 210

x = 210-195

x = 15