Question

In a parking lot, the guard observes that one tenth of the total cars parked are yellow in color. The guard went out to have some tea and when he returned, he saw that one new car had been parked in the lot and now, the red cars are one ninth of the total number of cars. How many cars are there in the parking lot now?

Answer 1

Let the total number of cars in the parking be X
Let Yellow Cars be Y
Thus  
Y = X/10
Let Red Cars be R

So   according to question
R = (X+1)/9
Thus

Total cars  = X/10 + (X+1)/9
                = (19X + 10)/90