Given:
Violinists : Cellists = 7:3.
Number of violinists in the school orchestra = 21
To find:
The combined number of cellists and violinists.
Solution:
Let the number of violinists and cellists in the school orchestra are 7x and 3x respectively.
Then, combined number of cellists and violinists is
...(i)
Number of violinists in the school orchestra = 21
Divide both sides by 7.
Now, the combined number of cellists and violinists is
[Using (i)]
Therefore, the combined number of cellists and violinists is 30.