Sports Motorbike

[Manonamission]

Hello,

A red sports motorbike crosses a juice shop outlet at 30 kmph at 11 AM in the morning.
Another blue sports motorbike riding at a higher speed,46 kmph crosses the same juice outlet at 11:30 AM.
At what time blue sports motorbike will cross over red sports motorbike?

Regards,
MoM

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Hi MoM,

When posting GMAT questions, you should make sure to post the ENTIRE prompt (along with the 5 answer choices). In many cases, the answers provide a 'clue' as to how you might go about solving the prompt (or they might be written in such a way as to allow you to avoid doing lots of calculations). Without those answers, we're forced to solve this mathematically.

This is an example of a 'chase down' question. Since the second bike is moving faster than the first, then that second bike is 'gaining' on the first. Assuming the two bikes maintain their constant speeds, then the second bike will 'catch up' 46-30 = 16 km per hour on the first bike. The first bike crossed the shop at 11am, and it has a 1/2 hour 'head start' on the second bike. At it's speed (30 km/hour), that 1/2 hour lead puts that bike (1/2)(30) = 15 km ahead of the second bike.

The second bike is gaining 16 km/hour on the first bike, so it would take 15/16 of an hour to catch the first bike.

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

[Manonamission]

Hi MoM,

When posting GMAT questions, you should make sure to post the ENTIRE prompt (along with the 5 answer choices). In many cases, the answers provide a 'clue' as to how you might go about solving the prompt (or they might be written in such a way as to allow you to avoid doing lots of calculations). Without those answers, we're forced to solve this mathematically.

This is an example of a 'chase down' question. Since the second bike is moving faster than the first, then that second bike is 'gaining' on the first. Assuming the two bikes maintain their constant speeds, then the second bike will 'catch up' 46-30 = 16 km per hour on the first bike. The first bike crossed the shop at 11am, and it has a 1/2 hour 'head start' on the second bike. At it's speed (30 km/hour), that 1/2 hour lead puts that bike (1/2)(30) = 15 km ahead of the second bike.

The second bike is gaining 16 km/hour on the first bike, so it would take 15/16 of an hour to catch the first bike.

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

Hello Rich,

Thanks a lot for this explanation.

And I will keep in mind your advise regarding entire prompt next time when I post a query.

Thanks
MoM