Add. 17. (+5) + (-2) + (-1)
18. (-7) + (-6) + (-2)
19. (+11) + (-9) + (-4)
20. (+4) + (-8) + (+6)

What is the volume of this square pyramid?

Abox contains 1 plain pencil and 4 pens. a second box contains 5 color pencils and 5 crayons. one item from each box is chosen at random. what is the probability that a plain pencil from the first box and a color pencil from the second box are selected? write your answer as a fraction in simplest form.

Suppose that sahil knows that 45 people with ages of 18 to 29 voted. without using a calculator, he quickly says then 135 people with ages of 30to 49 voted. is he correct? how might sohil have come up with his answer so quickly?