  # A Glossary of Common Words

This list includes various words and phrases that the children entering Problem Challenge are assumed to understand. We advise teachers to ensure that all children are familiar with their meanings before the start of the Problem Challenge competition. You may wish to review these terms before each Set.

 Perimeter The boundary of a shape.Also, the distance measured around a shape. A man walks around the perimeter of a lake.The perimeter of a 4 cm by 5 cm rectangle is 18 cm. Whole number A number from the set {0, 1, 2, 3, 4, ...}. 12 is a whole number.3.8 is not a whole number. Counting number A number from the set {1, 2, 3, 4, ...}. 12 is a counting number.0, –1 and 4.1 are not counting numbers. Sum The result of adding two or more numbers together. The sum of 3, 4 and 5 is 12.The sum of the first 10 counting numbers is 55. Product The result of multiplying two or more numbers together. The product of 3, 4 and 5 is 60.The product of 2 with any whole number is always even. Multiple A multiple of a number is the product of that number with a whole number. 12 is a multiple of 3 (since 12 = 3 × 4).100 is a multiple of 20 (since 100 = 20 × 5).24 is not a multiple of 9. Divisible A whole number is divisible by another number if the first is a multiple of the second. 12 is divisible by 3.100 is divisible by 20.24 is not divisible by 9. Factor If a whole number is divisible by another whole number, the second is a factor of the first. 3 is a factor of 12.20 is a factor of 100.9 is not a factor of 24.The number 28 has 6 factors (namely 1, 2, 4, 7, 14, 28). Prime number A whole number greater than 1 whose only factors are 1 and the number itself. The first ten prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.