Question

how to find this question plz tell in detail

Answer 1

Acc to me,

total students 20

average = (height of 1st student + 2nd +3rd +.....20)/total no. of height

it is given  10 students = 150cm

6=142cm

4=132cm

I previously tell the formula

height of (1st + 2nd + 3rd.....20)

you have given 10 student each of height is 150 cm so

if you put height of ten student in formula then

150 +150+150...10 times

If you want to add 10 times just add or

150 *10

1500----it is a sum of height from (1st +2nd+3rd--to 10th)

just do same and find other total 6 students height

6*142=852cm

and do same for 4 students

4*132=528cm

Put total height in formula

(1st+2nd+....10+11+12+...16+17+..20)/20

put sum from 1st to 10 students

1500

11 to 16

852

16 to 20

528

=(1500+852+528)/20

=2880/20

=144 Ans

I hope it help