黄皮数学p105-Q19

evelyn205205

IF C is the temperature in degrees Celsius and F is the temperature in degrees Fahrenheit, then the relationship between temperatures on the two scales is expressed y the equation 9C=5(F-32) .On a day when the temperature extremes recorded at a certain weather station differed by 45 degrees on the Fahrenheit scales, by how many degrees is the temperature extremes differ to the Celsius scale?

A．65/9
B．13
C．25
D．45
E．81

答案是C。
黄皮书上额解释是：根据公式，得：△C=5/9△F。
我疑惑的是这个式子是怎么由9C=5(F-32) 得到的？

sdcar2010

9C1=5(F1-32) (1)

9C2=5(F2-32) (2)

(1) - (2) : 9(C1-C2)=5(F1-F2)  So △C = (C1 - C2) = (5/9)*(F1-F2) = △F

Third grade math.

evelyn205205

9C1=5(F1-32) (1)

9C2=5(F2-32) (2)

(1) - (2) : 9(C1-C2)=5(F1-F2)  So △C = (C1 - C2) = (5/9)*(F1-F2) = △F

Third grade math.

-- by 会员 sdcar2010 (2011/6/23 22:43:12)

ok。我想知道为什么这么做，就是你对这道题的思路是什么？
因为我没有理解这道题。

sdcar2010

Then it is middle school algebra. y=ax + b