2What is Mathcounts?Mathcounts is a nationwide math competition held in various areas of the United States.Every year, usually around February, Microsoft hosts the Lake Washington chapter competition and the Washington state competition.The purpose of Mathcounts is to build student passion in math.
3StructureSprint Round – 30 questions , 1 point per question, 40 minutes in total. Counts for your individual score and team scoreTarget Round – 8 rounds, 2 questions per round, 2 points per questions, and 6 minutes per round. Counts for your individual score and team score.Team Round – 10 questions, 2 points per question, 20 minutes in total. Counts for your team score.Countdown Round – Top students compete in fast-paced problem solving.
4What should I study?Mathcounts is based off the middle school math curriculum. However, your common core knowledge will not be enough to succeed in MathcountsCombinatoricsAlgebraGeometryNumber TheoryUse your resources (AOPS textbook, mathisfun, your coach, etc.)
5How to succeed in Mathcounts Work HardEasier said then done, studying hard is the key to success in all areas. The key here is to learn concepts and problem solving from past problems and books.Work SmartTake it little by little. I recommend spending about 20 minutes on weekdays to just review some knowledge. Keep a journal to record progress and things you’ve learned.Use your resources. You have so many resources, it would be a shame not to use them. AOPS Volume 1, online problems, and your coach our all ways to learn techniques and tips for Mathcounts success.
6Mathcounts prep week 1 What we will cover Art of Problem Solving Volume 1:-Chapter 4 (proportions)-Chapter 5 (using the integers)-Intro to Chapter 7 (Special factorizations and clever manipulations)-Intro to Chapter 24 (Sequences and series)-Intro to Quadratic Equations, if time allows
7Chapter 4: Proportions Preview: Direct relationship – The quotient of two quantities is a constant, when one increases so this the other, when one decreases the other decreases as well.Inverse relationship – The product of two quantities is a constant, when one increases the other decreases.12 inches = 1 foot 10 cm = 1 meter5280 feet = 1 mile 3 feet = 1 yard.
8Some practice problems 57. The population of a town increases 25% during By what percent must it decrease the following year to return to the population it was at the beginning of 1991?60. If the ratio of 2x – y to x + y is 2 : 3, find the ration x : y.70. The wages of 3 men for 4 weeks is $108. At the same rate of pay, how many weeks will 5 men work for $135?82. If p is 50% of q and r is 40% of q, what percent of r is p?
9The house worker problem Example 4-5. It takes 3 days for 4 people to paint 5 houses. How long will it take 2 people to paint 6 houses?Solution: First we identify that the amount of work and time put into the job is directly proportional to the completion of the job. Thus, we can set up an equation.ℎ𝑜𝑢𝑠𝑒𝑠 𝑝𝑒𝑜𝑝𝑙𝑒 𝑑𝑎𝑦𝑠 = 5 126 2 𝑑𝑎𝑦𝑠 = 5 12When we cross-multiply, we get 10d = 72, thus d = 36/5.
10The A and B working together problem Example Pipe A can fill a pool in 5 hours, while pipe B can fill it in four. How long will it take for the two to fill the pool if both are operating at the same time?Solution: How can we solve this problem using algebra?Well, 𝑥 =1 where x is the answer.The question is, how does this work? ¼ and 1/5 represent is the amount each pipe can fill in one hour. Thus, ¼+ 1/5 is the amount they can complete in one hour. 1 represents 100% of the job being done. Therefore, the number of hours, x, is 1/( ). To compute this, add = Dividing a number into one is called taking a reciprocal. We take a reciprocal by flipping the numerator and denominator, thus the answer is 20/9.
11Algebraic sums problem 54. When three numbers are added two at a time, the sums are 29, 46, 53. What is the sum of all three numbers?
12Chapter 4 SummaryKnow direct and inverse relationships and when to apply themUnderstand the concept of percent and decimalsRemember conversion factorsAlgebraic equations can be very useful when dealing with proportionsThe house worker problemThe A and B working together problemAlgebraic sums problem
13Chapter 5: Using the Integers Preview:Divisibility rules (1-11 except 7)Modular arithmeticBase numbersPrime FactorizationLeast Common Multiple and Greatest Common Factor
14Some Practice Problems 84. Find the GCF of 36, 27, and 45.92. Find the value of digit A if the five-digit number 12A3B is divisible by 4 and 9, and A≠B.94. How many ways can a debt of $69 be paid using only $5 bills and $2 bills.97. When n is divided by 5, the remainder is 1. What is the remainder when 3n is divided by 5?
15Base Numbers Converting to base 10 Converting from base 10 Convert 212 base 3 into base 10Convert 234 base 5 into base 10Convert 123 base 6 into base 10Converting from base 10Convert 345 into base 4Convert 278 into base 3Convert 122 into base 2
16Chinese Remainder Theorem Problem 91. Find the smallest possible integer which when divided by 10 leaves a remainder of 9, when divided by 9 leaves a remainder of 8, by 8 leaves a remainder of 7, etc., down to where, when divided by 2, it leaves a remainder of 1.
17Solution to Chinese Remainder Theorem Problem Hint: What is the Least Common Multiple of 1-10.Solution: Wow, seems complicated at first. Whenever I see something complicated I read the problem repeatedly until I find something very unique. In this problem, I noticed that the remainder is always 1 smaller than the divisor, ex. 10-9=8-7=2-1=1. How does that help us? Well, if we find the Least Common Multiple of numbers 1-10 and subtract 1, it is going to meet the requirements. You see, if we did not subtract 1, the remainders would be 10, 9, 8 , 7…., 1 which is the same thing as 0. If we subtract 1, the remainder becomes one smaller than the divisor. Thus, the LCM – 1 = 2520 – 1= 2519.
18Primes What is the prime factorization of 320? How many factors does 320 have?What is the LCM of 27, 36, and 45?What is the GCF of 27, 36, and 45?
19Chapter 5 SummaryKnow how to find the GCF and LCM of a list of numbersDivisibility Rules can be applied in many waysKnow how to convert from and to base 10.Chinese Remainder Theorem problemPrimes are very important
20Chapter 7: Special Factorizations and Clever Manipulations (intro) PreviewDifference of squares conceptSum of Squares concept
21Some practice problems 138. Given that = , 𝑓𝑖𝑛𝑑139. What is the sum of the prime factors of −1?143. Factor 𝑥 12 − 𝑦 12 as completely as possible with integral coefficients and integral exponent.
22Chapter 24: Sequences and Series (Intro) Preview:Arithmetic SequenceGeometric SequenceInfinite SequenceBasic Sum formulas
23Fundamental Sum Problem 1.What is the sum of the first n counting numbers?Solution:Find the number of terms in the sequenceFind the average of the terms in the sequenceThe definition of average, or mean, is 𝑠𝑢𝑚 𝑜𝑓 𝑡𝑒𝑟𝑚𝑠 # 𝑜𝑓 𝑡𝑒𝑟𝑚𝑠 , therefore we multiply the answers to the first two steps.𝑛 𝑛 Note: This formula is extremely important!
24Some Practice Problems 1. What is the sum of the first 10 counting numbers?3. Evaluate …… + 20.5. What is the sum of the first 50 odd numbers?6. Evaluate (-10) + (-9) + (-8) …
25Next week Preview for next week: Slope and y-intercept Graphing Linear functionsThe Quadratic Formula 𝑥= −𝑏± 𝑏 2 −4𝑎𝑐 2𝑎Factoring QuadraticVieta’s FormulaMore counting and probability
26HomeworkPurchase the Art of Problem Solving Volume 1: the basics textbook and solution manual. It is listed as $42 on AOPS and may be cheaper on AmazonGet started on the assigned AOPS readingsGo to for past AMC 8 problems and solutions.Go to mathisfun.com to review some of this week’s topics and to prepare for next week’s topicsHave a Happy Thanksgiving!