A certain quantity is measured on two different scales, the R scale and the S scale, that are related linearly. Measurements on the R scale of 6 and 24 correspond to the measurements on the S scale of 30 and 60 respectively. What measurement on the R scale corresponds to a measurement of 85 on the S scale?  Choose the correct choice from the following answers:
A) 39  B) 41  C) 43  D) 45  E) 47
A change of +18 on the R scale is a change of +30 on the S scale.   R = (18/30)*S + K = 3S/5 + K   6 = 3(30)/5 + K   K = -12   R = 3S/5 - 12   R = 3(85)/5 - 12 = 51-12= 
<gadget id="calculator">51-12</gadget>
<output>39</output>
39   The answer is 39.
<result>A</result>
A certain quantity is measured on two different scales, the R scale and the S scale, that are related linearly. Measurements on the R scale of 6 and 24 correspond to the measurements on the S scale of 30 and 60 respectively. What measurement on the R scale corresponds to a measurement of 85 on the S scale?