Answer: New ratio = 3 : 2
Explanation:
Let the number of Girls be 'G'.
Given that the number of boys = 15
Ratio = G/15 = 4/3
Therefore,
3G = 4 x 15 = 60
G = 60/3 = 20
This means the number of girls = 20
Now,
One boy left the class, and one girl joined the class.
Therefore, the number of boys = 15 - 1 = 14
and, the number of girls = 20 + 1 = 21
New ratio = 21 / 14 = 3/2
New ratio = 3 : 2