Question

The marks obtained by 15 students in a class test are 12, 14, 07, 09, 23, 11, 08, 13, 11,
19, 16, 24, 17, 03, 20. Find :
(i) the mean of their marks.
(ii) the mean of their marks when the marks of each student are increased by 4.
(iii) the mean of their marks when 2 marks are deducted from the marks of each
student.
(iv) the mean of their marks when the marks of each student are doubled.
​

Answer 1

The obtained marks by 15 students arranging in ascending order,

03,07,08,09,11,11,12,13,14,16,17,19,20,23,24

(i) Mean=

15

03+07+08+09+11+11+12+13+14+16+17+19+20+23+24

=

15

207

=13.8

(ii) The new marks after increasing each student mark by 4 are,

07,11,12,13,15,15,16,17,18,20,21,23,24,27,28

Mean=

15

07+11+12+13+15+15+16+17+18+20+21+23+24+27+28

=

15

267

=17.8