by **Guest** » Thu Feb 28, 2013 9:31 am

Let x be the cost of the bike for A.

A sells it to B with a 28% loss

So B pays (1-28/100)x = 0.72x

B spends $1680, so he has now spent 0.72x+1680

B sells it to C making a 12.5% profit.

So B sells it to C for (1+12.5/100)(0.72x+1680) = 1.125(0.72x+1680) = 0.81x+1890

We are told C paid $35910,

So 0.81x+1890 = 35910

x = (35910 - 1890)/0.81 = 42000

So A paid $42000

(We could have also just worked backward. B sold the bike for 35910 and made 12.5% profit, so it originally cost him 35910/1.125 = 31920. B spent 1680 on repairs, so before repairs it cost him 31920-1680 = 30240. A sold it for 30240 which was a 28% loss, so it originally cost 30240/0.72 = 42000.)

Hope this helped,

R. Baber.