Ratio and Proportion Practice Test 4

The students in the three classes = 4 : 6 : 9
Students increased in each class = 12
Ratio change = 7 : 9 : 12
According to the statement,
4x+12:6x+12:9x+12 or a:b:c
We can write it as a : b : : b : c.
(4x+12):(6x+12) ::(6x+12):(9x+12)
Ratio change = 7 : 9 : : 9 : 12

(4x+12)(6x+12)

(6x+12)(9x+12)

=

7×9

9×12

(4x+12)

(9x+12)

=

7

12

x=4
Total number of students in three classes before the increase is =4x+6x+9x
=4×4+6×4+9×4=76