If the number of cars in city X this year is 520,800 which is 24% more

520 800=1,24*last year
last year is 520800/1,24=420000

\(\frac{520800}{124}*100\)

\(= 420,000\)

Thus, answer must be ( B ) 420,000

Hi All,

We're told that the number of cars in city X this year is 520,800 and that total is 24% more than there were in city X last year. We're asked for the number of cars that were there in city X last year. While the numbers in this prompt are not 'pretty', the answer choices are 'spaced out' enough that we can do a bit of estimation and some 'brute force' math to get to the answer.

To start, 24% of 100,000 = 24,000 (so a 24% increase would be 124,000 total cars). Thus, we can quickly map out increases of 100,000 cars...
200,000 + 48,000 = 248,000
300,000 + 72,000 = 372, 000
400,000 + 96,000 = 496,000
500,000 + 120,000 = 620,000

Since 520,800 is far closer to 496,000 than it is to 620,000, the total number of cars last year would be a bit more than 400,000. There's only one answer that matches...

Final Answer:

GMAT assassins aren't born, they're made,
Rich

Number of cars in City X this year = 520,800
It is 24% more than there were in City X last year.
So 520800 = 1.24 * cars last year
Cars last year = 520,800/ 1.24 = 420,000

Answer B