Let's call the 10 runners A B C D E F G H I J ABC ABD ABE ABF ABG ABH ABI ABJ ACB ACD ACE ACF ACG ACH ACI ACJ ADB ADC ADE ADF ADG ADH ADI ADJ AEB AEC AED AEF AEG AEH AEI AEJ AFB AFC AFD AFE AFG AFH AFI AFJ AGB AGC AGD AGE AGF AGH AGI AGJ AHB AHC AHD AHE AHF AHG AHI AHJ AIB AIC AID AIE AIF AIG AIH AIJ AJB AJC AJD AJE AJF AJG AJH AJI The above is 60 different ways, but now B C D E F G H I J have to come first, and the proses starts again, until we have covered them all. I'm not going to write them all out but in theory, there is 540 different ways. 9*60=540.
