freezer Posted October 17, 2007 Share Posted October 17, 2007 A and B ran a race of 480 m. In the first heat, A gives B a head start of 48 m and beats him by 1/10th of a minute. In the second heat, A gives B a head start of 144 m and is beaten by 1/30th of a minute. What is B’s speed in m/s? (A) 12 (B) 14 © 16 (D) 18 (E) 20 Could anybody give me a step by step solution? Thanks Quote Link to comment Share on other sites More sharing options...
ken_english Posted October 17, 2007 Share Posted October 17, 2007 is it 12 Quote Link to comment Share on other sites More sharing options...
notsofast Posted October 18, 2007 Share Posted October 18, 2007 Okay-see if this helps You need a condition where the operations performed on B's velocity in the first race will spit out the same result those in the second. A's velocity is constant. V=d/t (velocity is distance divided by time) Let's call A's time A (novel, I know) and B's time B A's velocity is 480/A's time; B's velocity is 480/B's time In the first race, A's time was better than B's by 6 seconds PLUS whatever time it took B to cover 48 meters. Mathematically, 480/A=480/B-48/B-60 simplified to 480/A=432/B-6 Second race: 480/A=336/B + 2 Set them equal and solve for B: 432/B-6=336/B+2 96/B=8 next 8B=96 B=12 Quote Link to comment Share on other sites More sharing options...
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