11. Select 3 cards from the set below which show the same value.
38. Zac has a set of 12 cards which are numbered from 1 to 12. He turns them face down and picks four cards.
Exactly three of the four cards are multiples of three. Exactly three of the four cards are odd numbers. The total of the four cards is less than 20.
What must the four cards be?
42. Factors are numbers that divide into another number exactly. For example, the factors of 28 are 1, 2, 4, 7, 14 and 28.
28 is called a perfect number because the factors of 28, not including the number 28 itself, add up to 28. So, 1 + 2 + 4 + 7 + 14 = 28.
a. i. Find all the factors of 12, not including 12.