Number series

Hand out a sheet of rough paper to each student.

When the students are ready, say:

This paper is for any rough working you want to do. Do not write in the Student Booklet. Now look at page 36 and follow while I read the directions.

Pause and check all the students are on the right page, and then read:

Each of these questions shows a series of numbers. You have to work out the rule or rules used to arrange the numbers. Then decide what number should come next in the series. Look at the example below.

Example

Look at the numbers and work out how the series is arranged. Each number is one lower than the number before it. Using this rule, think about which number should come after 12.  [Pause] As 12 minus 1 is 11, the right answer is C, 11. This is how you would show the answer. [Pause and indicate the example in the Student Booklet.]

Now try some practice questions. Mark your answer choices by filling in the correct box on the Answer Sheet. Remember, if you want to change your answer, rub out your first choice and mark your new letter choice.

 

Practice 1

Practice 2

Pause while the students choose their answers. Walk around the room, checking to make sure they are marking their answers correctly. Clear up any difficulties. Then continue as follows:

The answer to practice question 1 is F, 25, because the rule for this series is to add 5 to each number, and 20 plus 5 is 25.

The answer to practice question 2 is Q, 15. The easiest way to answer this question is to notice that there are two number patterns. The first, third and fifth numbers are going down by 1 each time: 18, 17, then 16. The numbers in between them are going up by two each time: 5, 7, then 9. This means the next number must be 16 minus 1, giving 15.

Are there any questions?

Answer any questions, and then read:

Do all of the questions on this test the same way. Try to answer every question.

You will have eight minutes to work on this test.

Turn over the page and begin. Work until you reach the stop sign at the end of the test.

Start your stopwatch or note the exact time to the nearest second on your watch or clock. Note this time on your Time Chart, and then add exactly eight minutes and fill in the stopping time.

While the test is in progress, walk around the room to make sure that all the students are marking their answers by drawing a line across the letters and that no one has turned to a page they should not be on. Encourage any students who finish early to check their answers. After exactly eight minutes, say:

Stop. Put your pencils down and turn to the next page.

Collect the rough paper.