Wll not just this question, but whenever you need to find average, you have to:
Wait, for example let's take ur question:
1st step we will add up all the values aka heights:
5.4+6.12+7.02+4.9+6.25=29.69
And then how many values did you take???
Its, 5 values
1st value= 5.4
2nd value=6.12
aaand so on....
However, then we will have to divide the sum by no.of values
29.69÷5=5.938
Aaand this is your FINAL ANSWER
Done!!!!
Hope I helped you!!!