SAT数学：今日份的5道练习题(附答案和解析)

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SAT数学练习题1：

In 2004, the number of people aged 16 years orolder in the United States was

approximately 223357000. According to the Bureau of Labor Statistics, at that

time 66% of the populationaged 16 and older was employed, and women made up

about 46.4% of this category. Approximately how many women aged 16 and older

were employed in 2004?

A.68400000

B.104000000

C.147400000

D.157000000

答案：A

解析：

Choice A is correct. The number of people aged 16 and older who were employed

in the United States in 2004 can be found by calculating 66% of 223357000.

66% of 223357000 can be found as follows:

0.66*223357000=147415620

Hence 147415620 people aged 16 or older were employed in the United States in

2004.

Of this number, 46.4% were women. To calculate the number of women in this

age group whowere employed, find 46.4% of 147415620:

0.464*147415620=68400847.68

Therefore, approximately 68400000 women aged 16 and older were employed in

the UnitedStates in 2004.

SAT数学练习题2：

ax+5=4x-3

In the linear equation shown above, a is aconstant. If the equation has no

solution, what is the value of a?

A.1

B.2

C.3

D.4

答案：D

解析：

Choice D is correct. A linear equation in onevariable will have no solution

if the equationreduces to an equation of the form:

ax+b=cx+d,

where a=c and b≠d.

Therefore, if a=4, the equation 4x+5=4x-3 yields 5=-3. This is not true for

any values of xand therefore this value of a results in an equation with no

solutions.

SAT数学练习题3：

The flow of water going over the Horseshoe Falls atNiagara Falls is about

2271240 liters per second (L/s). How much water goes over the Horseshoe Falls in

cubic meters per minute (m^3/min), rounded to the nearest whole number?

(Note: 1m^3=1000L)

A.2271m^3/min

B.13627m^3/min

C.136274m^3/min

D.13627400m^3/min

答案：C

SAT数学练习题4：

A circle in the xy-plane has its center at (-100,221) and a diameter of 17.

Which of the following is anequation of the circle?

A.(x+100)^2+(y-221)^2=7

B.(x+100)^2+(y-221)^2=2

C.(x-100)^2+(y+221)^2=7

D.(x-100)^2+(y+221)^2=2

答案：A

解析：

The formula for a circle with a center at (h,k) and aradius of r is:

(x-h)^2+(y-k)^2=r^2

The length of the radius is half of the length of thediameter.

1/2*17=8.5

Using the coordinates of the center and the length of the radius of this

circle in the equationyields: (x-(-100))^2+(y-221)^2=8.5^2

In standard form, the equation of this circle is:

(x+100)^2+(y-221)^2=72.25

SAT数学练习题5：

During the process of radioactive decay, a "parent" material produces a new

"daughter" material, whichfurther decays into a stable material. During an

experiment involving radioactive decay, themass M, in micrograms, of daughter

material changes over time t, measured in hours asshown in the graph above. What

is the significance of the point shown on the graph?

A. The point shows the mass of the daughter material at the beginning of the

experiment.

B. The point shows the mass of the daughter material when the mass was

increasing at itsfastest rate.

C. The point shows the amount of time the daughter material takes to decay

into stablematerial.

D. The point shows the maximum mass of the daughter material and the number

of hourssince it was created that its mass reached this maximum.

答案：D

解析：

Choice D is correct. The point indicated is the highes官方真题Officialint on the graph.

Since t represents the time inhours since the daughter material was created and

Mrepresents the mass of the daughter material, thepoint shows the values of t

and M when M is greatest. Therefore, the point shows the maximummass of the

produced substance and the number of hours since it was created that its

massreached this maximum.

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