megafan wrote:

Thanks Marcab. I made a silly mistake when taking the average with the reciprocal and arrived at 8x/5, which of course should be 2x/5. Anyway, I tend to make these silly mistakes once in a while, especially when I am doing the Math in my head. I will practice to make good use of my scratch paper from now.

Bad idea! Try to stick to doing the calculations in your mind till it becomes second nature. Then you will feel that writing down is too cumbersome. Initially, there will be more errors but later on, you will get very efficient.

Also, if trying to solve orally, making equations mentally isn't the appropriate approach. Take numbers instead:

So there is a 5 and a 3 in the denominator.

Say ridership in June = 15

Ridership in July = (3/5)*15 = 9

Ridership in Aug = (1/3)*9 = 3

Avg ridership in July and Aug = 6

Required answer = 15/6 = 5/2

Now this can be easily done in your mind. You can write 15, 9, 3 and 6 on your scratch pad if you wish but that should be just to ensure that you don't lose focus.

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