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Question bank AMC12 1970

Exam papers

35 questions

Question 1

The fourth power of $\sqrt{1+\sqrt{1+\sqrt1}}$ is:
  1. $\sqrt2+\sqrt3$
  2. $\tfrac12(7+3\sqrt5)$
  3. $1+2\sqrt3$
  4. $3$
  5. $3+2\sqrt2$

Question 2

A square and a circle have equal perimeters. The ratio of the area of the circle to the area of the square is:
  1. $\frac{4}{\pi}$
  2. $\frac{\pi}{\sqrt2}$
  3. $\frac{4}{1}$
  4. $\frac{\sqrt2}{\pi}$
  5. $\frac{\pi}{4}$

Question 3

If $x=1+2^p$ and $y=1+2^{-p},$ then $y$ in terms of $x$ is:
  1. $\dfrac{x+1}{x-1}$
  2. $\dfrac{x+2}{x-1}$
  3. $\dfrac{x}{x-1}$
  4. $2-x$
  5. $\dfrac{x-1}{x}$

Question 4

Let $S$ be the set of all numbers which are the sum of the squares of three consecutive integers. Then we can say that:
  1. No member of $S$ is divisible by $2$
  2. No member of $S$ is divisible by $3$ but
    some member is divisible by $11$
  3. No member of $S$ is divisible by $3$ or by $5$
  4. No member of $S$ is divisible by $3$ or by $7$
  5. None of these

Question 5

If $f(x)=\dfrac{x^4+x^2}{x+1},$ then $f(i),$ where $i=\sqrt{-1},$ is equal to:
  1. $1+i$
  2. $1$
  3. $-1$
  4. $0$
  5. $-1-i$

Question 6

The smallest value of $x^2+8x$ for real values of $x$ is:
  1. $-16.25$
  2. $-16$
  3. $-15$
  4. $-8$
  5. None of these

Question 7

Inside square $ABCD$ with side $s,$ quarter-circle arcs with radii $s$ and centers at $A$ and $B$ are drawn. These arcs intersect at a point $X$ inside the square. How far is $X$ from side $CD?$
  1. $\tfrac12s(\sqrt3+4)$
  2. $\tfrac12s\sqrt3$
  3. $\tfrac12s(1+\sqrt3)$
  4. $\tfrac12s(\sqrt3-1)$
  5. $\tfrac12s(2-\sqrt3)$

Question 8

If $a=\log_8 225$ and $b=\log_2 15,$ then:
  1. $a=\frac{b}{2}$
  2. $a=\frac{2b}{3}$
  3. $a=b$
  4. $b=\frac{a}{2}$
  5. $a=\frac{3b}{2}$

Question 9

Points $P$ and $Q$ are on line segment $AB,$ and both points are on the same side of the midpoint of $AB.$ Point $P$ divides $AB$ in the ratio $2:3,$ and $Q$ divides $AB$ in the ratio $3:4.$ If $PQ=2,$ then the length of segment $AB$ is:
  1. $12$
  2. $28$
  3. $70$
  4. $75$
  5. $105$

Question 10

Let $F=0.4818181\ldots$ be an infinite repeating decimal with the digits $8$ and $1$ repeating. When $F$ is written as a fraction in lowest terms, the denominator exceeds the numerator by:
  1. $13$
  2. $14$
  3. $29$
  4. $57$
  5. $126$

Question 11

If two factors of $2x^3-hx+k$ are $x+2$ and $x-1,$ the value of $|2h-3k|$ is:
  1. $4$
  2. $3$
  3. $2$
  4. $1$
  5. $0$

Question 12

A circle with radius $r$ is tangent to sides $AB,$ $AD,$ and $CD$ of rectangle $ABCD$ and passes through the midpoint of diagonal $AC.$ The area of the rectangle, in terms of $r,$ is:
  1. $4r^2$
  2. $6r^2$
  3. $8r^2$
  4. $12r^2$
  5. $20r^2$

Question 13

Given the binary operation $*$ defined by $a*b=a^b$ for all positive numbers $a$ and $b.$ Then for all positive $a,$ $b,$ $c,$ $n,$ we have:
  1. $a*b=b*a$
  2. $a*(b*c)=(a*b)*c$
  3. $a*(b^n)=(a*n)*b$
  4. $(a*b)^n=a*(bn)$
  5. None of these

Question 14

Consider $x^2+px+q=0,$ where $p$ and $q$ are positive numbers. If the roots of this equation differ by $1,$ then $p$ equals:
  1. $\sqrt{4q+1}$
  2. $q-1$
  3. $-\sqrt{4q+1}$
  4. $q+1$
  5. $\sqrt{4q-1}$

Question 15

Lines in the $xy$-plane are drawn through the point $(3,4)$ and the trisection points of the line segment joining the points $(-4,5)$ and $(5,-1).$ One of these lines has the equation:
  1. $3x-2y-1=0$
  2. $4x-5y+8=0$
  3. $5x+2y-23=0$
  4. $x+7y-31=0$
  5. $x-4y+13=0$

Question 16

If $F(n)$ is a function such that $F(1)=F(2)=F(3)=1,$ and such that $$
F(n+1)=\frac{F(n)F(n-1)+1}{F(n-2)}
$$ for $n\ge3,$ then $F(6)$ is equal to:
  1. $2$
  2. $3$
  3. $7$
  4. $11$
  5. $26$

Question 17

If $r\gt0,$ then for all $p$ and $q$ such that $pq\ne0$ and $pr\gt qr,$ we have:
  1. $-p\gt-q$
  2. $-p\gt q$
  3. $1\gt-\frac{q}{p}$
  4. $1\lt \frac{q}{p}$
  5. None of these

Question 18

$\sqrt{3+2\sqrt2}-\sqrt{3-2\sqrt2}$ is equal to:
  1. $2$
  2. $2\sqrt3$
  3. $4\sqrt2$
  4. $\sqrt6$
  5. $2\sqrt2$

Question 19

The sum of an infinite geometric series with common ratio $r$ such that $|r|\lt1$ is $15,$ and the sum of the squares of the terms of this series is $45.$ The first term of the series is:
  1. $12$
  2. $10$
  3. $5$
  4. $3$
  5. $2$

Question 20

Lines $HK$ and $BC$ lie in a plane. $M$ is the midpoint of line segment $BC,$ and $BH$ and $CK$ are perpendicular to $HK.$ Then we:
  1. always have $MH=MK$
  2. always have $MH\gt BK$
  3. sometimes have $MH=MK$ but not always
  4. always have $MH\gt MB$
  5. always have $BH\lt BC$