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2010 AMC 10B

Question 1

What is the value of the following expression? $$
100(100-3)-(100 \cdot 100-3)
$$
  1. $-20{,}000$
  2. $-10{,}000$
  3. $-297$
  4. $-6$
  5. $0$

Question 2

Makayla attended two meetings during her $9$-hour work day. The first meeting took $45$ minutes and the second meeting took twice as long. What percent of her work day was spent attending meetings?
  1. $15$
  2. $20$
  3. $25$
  4. $30$
  5. $35$

Question 3

A drawer contains red, green, blue, and white socks with at least $2$ of each color. What is the minimum number of socks that must be pulled from the drawer to guarantee a matching pair?
  1. $3$
  2. $4$
  3. $5$
  4. $8$
  5. $9$

Question 4

For a real number $x,$ define $\heartsuit(x)$ to be the average of $x$ and $x^2.$ What is the value of the following expression? $$
\heartsuit(1)+\heartsuit(2)+\heartsuit(3)
$$
  1. $3$
  2. $6$
  3. $10$
  4. $12$
  5. $20$

Question 5

A month with $31$ days has the same number of Mondays and Wednesdays. How many of the seven days of the week could be the first day of this month?
  1. $2$
  2. $3$
  3. $4$
  4. $5$
  5. $6$

Question 6

A circle is centered at $O,$ $\overline{AB}$ is a diameter and $C$ is a point on the circle with $\angle COB = 50^\circ.$ What is the degree measure of $\angle CAB?$
  1. $20$
  2. $25$
  3. $45$
  4. $50$
  5. $65$

Question 7

A triangle has side lengths $10,$ $10,$ and $12.$ A rectangle has width $4$ and area equal to the area of the triangle. What is the perimeter of this rectangle?
  1. $16$
  2. $24$
  3. $28$
  4. $32$
  5. $36$

Question 8

A ticket to a school play costs $x$ dollars, where $x$ is a whole number. A group of $9$th graders buys tickets costing a total of $\$48,$ and a group of $10$th graders buys tickets costing a total of $\$64.$ How many values for $x$ are possible?
  1. $1$
  2. $2$
  3. $3$
  4. $4$
  5. $5$

Question 9

Lucky Larry’s teacher asked him to substitute numbers for $a,$ $b,$ $c,$ $d,$ and $e$ in the expression $$
a-(b-(c-(d+e)))
$$ and evaluate the result. Larry ignored the parentheses but added and subtracted correctly and obtained the correct result by coincidence. The numbers Larry substituted for $a,$ $b,$ $c,$ and $d$ were $1,$ $2,$ $3,$ and $4,$ respectively. What number did Larry substitute for $e?$
  1. $-5$
  2. $-3$
  3. $0$
  4. $3$
  5. $5$

Question 10

Shelby drives her scooter at a speed of $30$ miles per hour if it is not raining, and $20$ miles per hour if it is raining. Today she drove in the sun in the morning and in the rain in the evening, for a total of $16$ miles in $40$ minutes. How many minutes did she drive in the rain?
  1. $18$
  2. $21$
  3. $24$
  4. $27$
  5. $30$

Question 11

A shopper plans to purchase an item that has a listed price greater than $\$100$ and can use any one of the three coupons. Coupon A gives $15\%$ off the listed price, Coupon B gives $\$30$ off the listed price, and Coupon C gives $25\%$ off the amount by which the listed price exceeds $\$100.$

Let $x$ and $y$ be the smallest and largest prices, respectively, for which Coupon A saves at least as many dollars as Coupon B or C. What is $y - x?$
  1. $50$
  2. $60$
  3. $75$
  4. $80$
  5. $100$

Question 12

At the beginning of the school year, $50\%$ of all students in Mr. Wells’ math class answered “Yes” to the question “Do you love math”, and $50\%$ answered “No.” At the end of the school year, $70\%$ answered “Yes” and $30\%$ answered “No.” Altogether, $x\%$ of the students gave a different answer at the beginning and end of the school year. What is the difference between the maximum and the minimum possible values of $x?$
  1. $0$
  2. $20$
  3. $40$
  4. $60$
  5. $80$

Question 13

What is the sum of all the solutions of the equation below? $$
x = |2x-|60-2x||
$$
  1. $32$
  2. $60$
  3. $92$
  4. $120$
  5. $124$

Question 14

The average of the numbers $1,$ $2,$ $3,$ $\cdots,$ $98,$ $99,$ and $x$ is $100x.$ What is $x?$
  1. $\dfrac{49}{101}$
  2. $\dfrac{50}{101}$
  3. $\dfrac{1}{2}$
  4. $\dfrac{51}{101}$
  5. $\dfrac{50}{99}$

Question 15

On a $50$-question multiple choice math contest, students receive $4$ points for a correct answer, $0$ points for an answer left blank, and $-1$ point for an incorrect answer. Jesse’s total score on the contest was $99.$ What is the maximum number of questions that Jesse could have answered correctly?
  1. $25$
  2. $27$
  3. $29$
  4. $31$
  5. $33$

Question 16

A square of side length $1$ and a circle of radius $\dfrac{\sqrt{3}}{3}$ share the same center. What is the area inside the circle, but outside the square?
  1. $\dfrac{\pi}{3}-1$
  2. $\dfrac{2\pi}{9}-\dfrac{\sqrt{3}}{3}$
  3. $\dfrac{\pi}{18}$
  4. $\dfrac{1}{4}$
  5. $\dfrac{2\pi}{9}$

Question 17

Every high school in the city of Euclid sent a team of $3$ students to a math contest. Each participant in the contest received a different score. Andrea’s score was the median among all students, and hers was the highest score on her team. Andrea’s teammates Beth and Carla placed $37$th and $64$th, respectively. How many schools are in the city?
  1. $22$
  2. $23$
  3. $24$
  4. $25$
  5. $26$

Question 18

Positive integers $a,$ $b,$ and $c$ are randomly and independently selected with replacement from the set $\{1, 2, 3,\dots, 2010\}.$

What is the probability that $abc + ab + a$ is divisible by $3?$
  1. $\dfrac{1}{3}$
  2. $\dfrac{29}{81}$
  3. $\dfrac{31}{81}$
  4. $\dfrac{11}{27}$
  5. $\dfrac{13}{27}$

Question 19

A circle with center $O$ has area $156\pi.$ Triangle $ABC$ is equilateral, $\overline{BC}$ is a chord on the circle, $OA = 4\sqrt{3},$ and point $O$ is outside $\triangle ABC.$ What is the side length of $\triangle ABC?$
  1. $2\sqrt{3}$
  2. $6$
  3. $4\sqrt{3}$
  4. $12$
  5. $18$

Question 20

Two circles lie outside regular hexagon $ABCDEF.$ The first is tangent to $\overline{AB},$ and the second is tangent to $\overline{DE}.$ Both are tangent to lines $BC$ and $FA.$ What is the ratio of the area of the second circle to that of the first circle?
  1. $18$
  2. $27$
  3. $36$
  4. $81$
  5. $108$