SAT数学Problem Solving练习题(3)
- 2017年07月21日14:23 来源:互联网
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Question #5: Celsius degrees can be transformed in Fahrenheit degrees by using the formula : °C=(5/9)· (°F-32). What is x, if x degrees Celsius is equal to x degrees Fahrenheit?
(a) 40
(b) -40
(c) -20
(d) 20
(e) -30
Answer: x = (5/9)· (x - 32).
9·x = 5·(x - 32).
In conclusion, x = -40C = -40F
Question #6: In the (x,y) plane, what is the equation of the line that passes through the points (0,5) and (4,0)?

(a) y = (5/4) · x + 4
(b) y = (4/5) · x - 4
(c) y = (4/5) · x + 4
(d) y = -(5/4) · x + 5
(e) y = (5/4) · x + 5
Answer: The equation of a line is y = m · x + n
First point, x = 0, y = 5, results in 5 = n
Second point: x = 4, y = 0, means 0 = m · 4 + n, or m = -n/4 or m= -5/4.
In conclusion, y = -(5/4) · x + 5 is the correct answer.