单选题
Life expectancy among adults 45 and 65 years of age by family income, sex, and race: United States, average annual 1979-89
单选题
A sequence of numbers begins 1, 1, 1, 2, 2, 3 and then repeats this pattern forever. What is the sum of the 135th, 136th, and 137th numbers in the sequence?
【正确答案】
C
【答案解析】Since the pattern has six digits, divide 135 by 6. The quotient is 22 and the remainder is 3. Since 22 × 6 = 132, the 132nd number completes the pattern for the 22nd time. So the 133rd, 134th, and 135th numbers are Is, and the 136th and 137th are 2s; and their sum is 1+2+2=5,
单选题
In the figure above, the diameter of the circle is 20 and the area of the shaded region is 80π. What is the value of a + b + c + d?
In the figure above, the diameter of the circle is 20 and the area of the shaded region is 80π. What is the value of a + b + c + d?
【正确答案】
E
【答案解析】Since the diameter of the circle is 20, the radius is 10 and the area is 100π. Since the area of the shaded region is 80π, it is [*] of the circle, and the white area is [*] of the circle. So the sum of the measures of the two white central angles is [*] of 360°, or 72°! The sum of the measures of all six angles in the triangles is 360°, so a + b + c + d= 360 -72 = 288.