Hands-on math!

Washington State Math Olympiad
Hints and Solutions
2014 Grade 8 Number Sense

Problem
Hint
1) Grandpa tells Nelli he has an investment in a fund that has a history of increasing in values by 6.2% every year. He has $32,000 invested in that fund. He asks her to compute how much the fund will earn him over five years if he makes no changes to his investment. Let V be the value of Grandpa's investment after 5 years.
V = P (1 + r)t where:
  P is the principal you start with
  r is the interest rate (specified as a decimal)
  t is the number of time periods
  • Compute the value of Grandpa's investment after 5 years:

  • Subtract the oroginal amount:

  • He will have earned _____________________

  • 2) A dime is 1.25x10-3 meter thick and is worth 1x 10-1 dollars. How many meters high is a stack of dimes worth 1x106 dollars? Express your answer in meters without using scientific notation.
    1. Determine the number of dimes in 1x106 dollars:


    2. Multiply boy the thickness of 1 dime:


    Problem
    Hint
    3) The numbers 1 - 32 can be represented with a set of five lights using the binary system. An "on" light is recorded with a 1, an "off" light is recorded with a 0. With the pattern given in the table, how would the number 23 be represented in 1's and 0's?
    1. Each binary digit, or "bit", starting on the right side, is a power of 2, so the first bit is 20 = 1, the second is 21 = 2, and so on up to the 5th bit which is 24 = 16
    2. Here's how you turn a decimal number into binary:
      1. Write down the decimal number.
      2. Divide the number by 2.
      3. Write the result underneath.
      4. Write the remainder on the right hand side.
        This will be 0 or 1.
      5. Divide the result of the division by 2 and again write down the remainder.
      6. Continue dividing and writing down remainders until the result of the division is 0.
        The most significant bit (MSB) is at the bottom of the column of remainders and the least significant bit (LSB) is at the top. Read the series of 1s and 0s on the right from the bottom up. This is the binary equivalent of the decimal number.
      The binary representation of 23 is ______________
    4) The Golden Ratio is the ratio of a Golden rectangle's length to width that is most pleasing to the eye. This ratio is
    (1 + √ 5) / 2. If a Golden Rectangle has width 2√ 5 , then what is its length? Give an exact answer leaving radicals in your answer if needed.
    Let L be the rectangle's length.
    Take the ratio of the rectangle's length to its width and set that equal to the golden ratio and solve for L.






    L = _________

    5) In the equation (2x)3(4x2)-2= 25 4-3 what is x?

    Combine the terms with x and also the constants and solve for x





    x = _______