Special Numbers

Transcript

Special NumbersThe "Special numbers" activity is a mathematical thinking exercise. The goal is to look at a group of four numbers and for each number, find a unique property that makes it "special" compared to the other three numbers in that specific box. There can be many different correct answers for each number. Let’s look at our box – and why each number could be special: 9 is special because it is the only single-digit number , or because it is the only multiple of 3. 16 is special because it is the only even number and the only multiple of 4. 25 is special as it is the only multiple of 5. 43 is special because it is the only prime number , or because it is the only number that is not a perfect square Below are some boxes with four numbers in each box. Within each box try to say how each number is special compared to the rest. Discuss with your classmates Let’s do it one by one Box 1: {5, 7, 12, 35} 5 could be special because it is the smallest number. 7 could be special because it is the only prime number whose multiples are not also in the set (35 is a multiple of 5). 12 could be special because it is the only even number. 35 could be special because it is the only number that is a product of two other numbers in the set (5 x 7). Box 4: {17, 27, 44, 65} 17 could be special because it is the only prime number. 27 could be special because it is the only odd composite number. 44 could be special because it is the only even number. 65 could be special because it is the only multiple of 5. Box 2: {3, 8, 11, 24} 3 could be special because it is the only prime factor of another number in the set (24). 8 could be special because it is the only perfect cube (23=8). 11 could be special because it is the only two-digit prime number. 24 could be special because it is the only number that is a multiple of two other numbers in the set (3 and 8). Box 3: {27, 3, 123, 31} 27 could be special because it is the only perfect cube (33=27). 3 could be special because it is the only single-digit number. 123 could be special because it is the only number with three digits. 31 could be special because it is the only two-digit prime number.