In a 100m race, A beats B by 20m. B beats C by 20m. What is the distan

Question

In a 100m race, A beats B by 20m. B beats C by 20m. What is the distance by which A beats C ?

A. 20
B. 36
C. 40
D. 50
E. cannot be determined

A beats B by 20 meters
A - 100
B - 80
A/B = 100/80

B beats C by 20 meters
Say in a 100-meter race, B -100
C - 80
B/C = 100/80

A/B*B/C = 100/80*100/80 = A/C = 100/64

So in a 100 meter race, A beats C by 36 meters.

B is the answer.

Vinit800HBS · Answer

B covers 80% of what A covers and C covers 80% of what B covers.

So, C will cover 80% of 80% Of distance that A covers I.e. 64%

Thus, C is lagging behind by (100-64)% of the race length.

Hence, C lags by 36meters

Posted from my mobile device

IP1992 · Answer

Distance ratio:
A:B=100:80=500:400

B:C=100:80=400:320

A Beats C in
500 m race by 180 meter
100 m race by (180*100/500)=36 meter.

Posted from my mobile device

GMATGuruNY · Answer

The prompt should state that the rates are constant

In a 100m race, A beats B by 20m. 
Since B is 20 meters behind A when A completes the 100-meter race, B travels 80 meters in the time it takes A to travel 100 meters:
 \frac{A}{B} = \frac{100}{80} = \frac{5}{4}

B beats C by 20m .
Since C is 20 meters behind B when B completes the 100-meter race, C travels 80 meters in the time it takes B to travel 100 meters:
 \frac{B}{C} = \frac{100}{80} = \frac{5}{4}

Thus:
 \frac{A}{C} = \frac{A}{B }* \frac{B}{C} = \frac{5}{4} * \frac{5}{4} = \frac{25}{16} = \frac{100}{64}

Since  \frac{A}{C} = \frac{100}{64} , C travels 64 meters in the time it takes A to complete the 100-meter race, with the result that A beats C by 36 meters.

B

samarpan.g28 · Answer

Hi. I could not see the question right below the timer. It was the solution provided by Chethan92 directly. Kindly help.

Bunuel · Answer

_______________________
Fixed the issue. Thank you!

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

In a 100m race, A beats B by 20m. B beats C by 20m. What is the distan

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Problem Solving (PS) Questions

In a 100m race, A beats B by 20m. B beats C by 20m. What is the distan

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards