2010 AMTNJ Contest – Solutions

advertisement

2010 AMTNJ Contest – Solutions

1) The probability that Larry gets a six on his first throw is . The probability that it is his second throw is . The probability that he gets a six on the throw is

This is a geometric series with first term , with common ratio

.

. Finding the sum using

gives .

2) 7 Let n be the largest of the numbers. If n is removed the average must be greater than

. If 1 is removed the average must be less than . Therefore

and , hence n = 69 or 70. Since numbers, n must equal 69. If n = 69 then the missing number must be 7, since

is the average of n-1

gives n = 7.

3) therefore and is the smallest angle.

gives ,

4) 3 . This is real, only if . Solving for n , gives n = 0, 1, or -1. Therefore, there are 3 possible values for n .

5) no solutions. Adding all the given equations and rearranging the terms results in

or squares that add to 175; therefore, there are no solutions.

. There are no perfect

6) and

Let x be the angle opposite the side of length c .

or . By the Law of Cosines:

. Therefore,

7) 5

Therefore,

. Since  ABO

=

60

°

, then and

8) 0 log(4)+log(f)-log(5)-log(g)-log(3)-log(d)+log(g)-log(6)-log(f)+log(9)+ log(h)+ log(5)+log(d)-log(2)-log(h)= [log(2)+log(2)]-log(3)-[log(2)+log(3)]-[log(3)+log(3)]-log(2)=0

9) If the hexagon is ABCDEF and Willie starts at vertex A, he will pass through B and C and end up halfway to point D, called that point P. Since AB = BC = 2 and then AC = . is a right triangle with right angle point C. By the Pythagorean theorem

10) Since , solving for q gives

.

11) 69 Adding the two equations gives

.

Therefore,

12) remainder of

Dividing gives a quotient of

. Since the remainder must be 0, and

and a

13) 16

; therefore, a =1 and b = -2.

Each of the four playoff games has 2 possible outcomes. For each sequence of 4 outcomes, the prizes are awarded different ways. Thus, there are possible outcomes.

14) 4 If opposite side a is acute, then by the Law of Cosines

and Therefore, solving the inequalities

and gives integer answers of 22, 23, 24, and 25.

15) Jan. 27 th . For geometric series, . Therefore,

and or n = 27.

,

Download