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1960 AMC 12

Question 1

If $2$ is a solution (root) of $x^3+hx+10=0,$ then $h$ equals:
  1. $10$
  2. $9$
  3. $2$
  4. $-2$
  5. $-9$

Question 2

It takes $5$ seconds for a clock to strike $6$ o’clock beginning at $6{:}00$ o’clock precisely. If the strikings are uniformly spaced, how long, in seconds, does it take to strike $12$ o’clock?
  1. $9\dfrac13$
  2. $10$
  3. $11$
  4. $14\dfrac23$
  5. none of these

Question 3

Applied to a bill for $\$10{,}000$ the difference between a discount of $40\%$ and two successive discounts of $36\%$ and $4\%,$ expressed in dollars, is:
  1. $0$
  2. $144$
  3. $256$
  4. $400$
  5. $416$

Question 4

Each of two angles of a triangle is $60^\circ$ and the included side is $4$ inches. The area of the triangle, in square inches, is:
  1. $8\sqrt3$
  2. $8$
  3. $4\sqrt3$
  4. $4$
  5. $2\sqrt3$

Question 5

The number of distinct points common to the graphs of $x^2+y^2=9$ and $y^2=9$ is:
  1. infinitely many
  2. four
  3. two
  4. one
  5. none

Question 6

The circumference of a circle is $100$ inches. The side of a square inscribed in this circle, expressed in inches, is:
  1. $\dfrac{25\sqrt2}{\pi}$
  2. $\dfrac{50\sqrt2}{\pi}$
  3. $\dfrac{100}{\pi}$
  4. $\dfrac{100\sqrt2}{\pi}$
  5. $50\sqrt2$

Question 7

Circle I passes through the center of, and is tangent to, circle II. The area of circle I is $4$ square inches. Then the area of circle II, in square inches, is:
  1. $8$
  2. $8\sqrt2$
  3. $8\sqrt\pi$
  4. $16$
  5. $16\sqrt2$

Question 8

The number $2.5252525\ldots$ can be written as a fraction. When reduced to lowest terms the sum of the numerator and denominator of this fraction is:
  1. $7$
  2. $29$
  3. $141$
  4. $349$
  5. none of these

Question 9

The fraction $$
\frac{a^2+b^2-c^2+2ab}{a^2+c^2-b^2+2ac}
$$ is (with suitable restrictions on the values of $a,$ $b,$ and $c$):
  1. irreducible
  2. reducible to $-1$
  3. reducible to a polynomial of three terms
  4. reducible to $\dfrac{a-b+c}{a+b-c}$
  5. reducible to $\dfrac{a+b-c}{a-b+c}$

Question 10

Given the following six statements:

$(1)$ All women are good drivers.

$(2)$ Some women are good drivers.

$(3)$ No men are good drivers.

$(4)$ All men are bad drivers.

$(5)$ At least one man is a bad driver.

$(6)$ All men are good drivers.

The statement that negates statement $(6)$ is:
  1. $(1)$
  2. $(2)$
  3. $(3)$
  4. $(4)$
  5. $(5)$

Question 11

For a given value of $k,$ the product of the roots of $$
x^2-3kx+2k^2-1=0
$$ is $7.$ The roots may be characterized as:
  1. integral and positive
  2. integral and negative
  3. rational, but not integral
  4. irrational
  5. imaginary

Question 12

The locus of the centers of all circles of given radius $a,$ in the same plane, passing through a fixed point, is:
  1. a point
  2. a straight line
  3. two straight lines
  4. a circle
  5. two circles

Question 13

The polygon(s) formed by $y=3x+2,$ $y=-3x+2,$ and $y=-2,$ is (are):
  1. an equilateral triangle
  2. an isosceles triangle
  3. a right triangle
  4. a triangle and a trapezoid
  5. a quadrilateral

Question 14

If $a$ and $b$ are real numbers, the equation $3x-5+a=bx+1$ has a unique solution $x$ [the symbol $a\ne0$ means that $a$ is different from zero]:
  1. for all $a$ and $b$
  2. if $a\ne2b$
  3. if $a\ne6$
  4. if $b\ne0$
  5. if $b\ne3$

Question 15

Triangle I is equilateral with side $A,$ perimeter $P,$ area $K,$ and circumradius $R$ (radius of the circumscribed circle). Triangle II is equilateral with side $a,$ perimeter $p,$ area $k,$ and circumradius $r.$ If $A$ is different from $a,$ then:
  1. $P:p=R:r$ only sometimes
  2. $P:p=R:r$ always
  3. $P:p=K:k$ only sometimes
  4. $R:r=K:k$ always
  5. $R:r=K:k$ only sometimes

Question 16

In the numeration system with base $5,$ counting is as follows: $1,$ $2,$ $3,$ $4,$ $10,$ $11,$ $12,$ $13,$ $14,$ $20,$ $\ldots$ The number whose description in the decimal system is $69,$ when described in the base $5$ system, is a number with:
  1. two consecutive digits
  2. two non-consecutive digits
  3. three consecutive digits
  4. three non-consecutive digits
  5. four digits

Question 17

The formula $N=8\cdot10^8\cdot x^{-\frac{3}{2}}$ gives, for a certain group, the number of individuals whose income exceeds $x$ dollars. The lowest income, in dollars, of the wealthiest $800$ individuals is at least:
  1. $10^4$
  2. $10^6$
  3. $10^8$
  4. $10^{12}$
  5. $10^{16}$

Question 18

The pair of equations $3^{x+y}=81$ and $81^{x-y}=3$ has:
  1. no common solution
  2. the solution $x=2,$ $y=2$
  3. the solution $x=2\dfrac12,$ $y=1\dfrac12$
  4. a common solution in positive and negative integers
  5. none of these

Question 19

Consider equation I: $x+y+z=46,$ where $x,$ $y,$ and $z$ are positive integers, and equation II: $x+y+z+w=46,$ where $x,$ $y,$ $z,$ and $w$ are positive integers. Then:
  1. $\mathrm{I}$ can be solved in consecutive integers
  2. $\mathrm{I}$ can be solved in consecutive even integers
  3. $\mathrm{II}$ can be solved in consecutive
    integers
  4. $\mathrm{II}$ can be solved in consecutive even integers
  5. $\mathrm{II}$ can be solved in consecutive odd integers

Question 20

The coefficient of $x^7$ in the expansion of $$
\left(\frac{x^2}{2}-\frac2x\right)^8
$$ is:
  1. $56$
  2. $-56$
  3. $14$
  4. $-14$
  5. $0$