Data Sufficiency

AAPL wrote:If a horse runs his first lap in 75 seconds, how long will it take the horse to complete three laps?

(1) Each lap the horse's speed decreased 20 percent from the previous lap.
(2) The horse will be racing against another horse whose speed increases 8% each lap and who completes three laps in 225 seconds.

The OA is A.

We need to know the speed or the time taken by the horse in each lap.

Statement 1: the speed relation for each lap is given. SUFFICIENT
Statement 2: data for another horse is given without any link. INSUFFICIENT

Hence, A is the correct answer.

Has anyone another strategic approach to solving this DS question? Regards!

Given: The horse runs his first lap in 75 seconds.

To find out: Time taken by the horse to complete three laps

Let's take each statement one by one.

(1) Each lap the horse's speed decreased 20 percent from the previous lap.

Time in the I lap = 75 sec.
Time in the II lap = 75 + 20% = 90 sec.
Time in the II lap = 90 + 20% = 108 sec.

Total time in three laps = 75 + 90 + 108 = 273 sec. Sufficient.

(2) The horse will be racing against another horse whose speed increases 8% each lap and who completes three laps in 225 seconds.

With this information, we can know the time taken in each lap by the rival horse, but no relation between the times of the horses is given. Insufficient.

The correct answer: A

Hope this helps!

-Jay
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