The average height of 30 students of a class is 165 cm. 5 new students with average height 172 cm join the class. What is the new average (in cm) of the class?
The total sum of heights of 30 students was 30 $$\times$$ 165, which is 4950 cm.
Now, 5 students with an average height of 172 cm joined the class, which makes the total height as 860+4950= 5810 cm.
The average height of the 35 students now will be $$\ \frac{\ 5810}{35}$$ = 166 cm.