Solution:Let the number of cars in showroom X, Y and Z be 5x, 7x and 8x respectively.
Number of petrol cars in showroom X = 5x × 36/100
=> 1.8x
Number of electric cars in showroom X = 5x - 1.8x
=> 3.2x
Now, let number of electric cars in showroom Y = a
Then, according to the question,
a/4 + a = 7x
5a/4 = 7x
a = (7x × 4)/5
a = 5.6x
So, number of petrol cars in showroom Y = 7x - 5.6x
=> 1.4x
Now, number of petrol cars in showroom Z = 8x × 9/25 => 2.88x
And, number of electric cars in showroom Z = 8x × 16/25 => 5.12x
Total number of petrol cars in all the showroom =
1.8x + 1.4x + 2.88x = 6.08x
Total number of electric cars in all the showroom =
3.2x + 5.6x + 5.12x = 13.92x
Thus, the required percentage = (13.92x - 6.08x)/13.92x × 100
= 7.84x/13.92x × 100 ≈ 56%
Hence, the required answer = 56% (Approximately)