Posted by ♫J.R.♫ on .
A tire shop that sells only one size of tire, .75 metres in diameter, decides to sell tires for big rigs that are 1.5 metres in diameter. If the cost of the .75 meter tires is $100.00 for four, how much will it cost for the 18 tires required for a big rig? Prices increase proportionally with size.
x = price for each big rig tire
Size Price/tire
0.75m $100/4 = $25.00 each
1.5m x
Solve for x:
0.75m/$25.00 = 1.5/x
0.75x = 1.5 * $25.00
0.75x = $37.50
x = $50.00/tire
Price for 18 tires = 18($50.00) = $900.00

Math 
Rezu,
Yup. It's $900.00