Approximately how many revolutions will be made by a car tire with a 13-inch diameter if the car travels 1⁄2 mile?
Select the correct option:  A) 120  B) 180  C) 772  D) 720  E) 1,440
Diameter of car tire = 13 inches   Radius of car tire = 6.5 inches = 6.5*2.54= 
<gadget id="calculator">6.5*2.54</gadget>
<output>16.51</output>
16.51 cm   Circumference of the car tire= 2*pi * 16.51 = 2 *3.14 *16.51= 103.68 cm   Distance traveled by car = .5 mile = .5 *1.6= 
<gadget id="calculator">.5 *1.6</gadget>
<output>0.8</output>
.8 km= 800 m = 8 * 10^4 cm   Number of revolutions =Distance traveled / Circumference of tire = 8 * 10^4 / 103.68 = 771.60   Since the answer choices are far apart we should use estimation in this question .   Ideally ,in the GMAT the conversion between units would be provided .   Answer 772
<result>C</result>
Approximately how many revolutions will be made by a car tire with a 13-inch diameter if the car travels 1⁄2 mile?