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? A. 3B. 4C. 5D. 6E. 7

A
B
C
D
E

【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 {{U}}135{{/U}}th numbers are Is, and the {{U}}136{{/U}}th and {{U}}137{{/U}}th are 2s; and their sum is {{U}}1{{/U}}+{{U}}2{{/U}}+{{U}}2{{/U}}=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? A. 144B. 216 C. 240 D. 270 E. 288

A
B
C
D
E

【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.