There are 150 books in kindergarten, two fifths of which are dressed up, and the rest are given to small classes and middle classes at a ratio of 4:5. How many books are given to the small class and the middle class respectively? Setting: the small class is 4a,

Then the middle shift is 5a.

The remaining books are 150×( 1-2/5 )=90.

From question 4a+5a=90.

Get a = 10,

That is, small class 4a=40 and middle class 5a=50.