6月数学JJ中GWD里相关的-两题

Q10:

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 measurements on the S-scale
of 30 and 60, respectively.  What
measurement on the R-scale corresponds to a measurement of 100 on the S-scale?

A.    
20

B.    
36

C.    
48

D.    
60

E.     
84

Ans：C

A.    
  0

B.    
–1

C.    
–2

D.    
–3

E.     
–4

Ans：D

第一题的算法：

因为线性相关，所以　Ｓ＝Ra +b

30=6a+b

60=24a+b

得a=5/3 b=20 得出原式　　Ｓ＝Ｒ＊５／３＋２０

代入Ｓ＝１００得Ｒ＝４８

谢谢！！！