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Lesson · Grade 7 · Mathematics

What the two numbers in 3n + 2 mean

  • Grade 7
  • Mathematics
  • 1 min 18 s
  • British Columbia
  • BC7-MA-39

A growing tile pattern follows the rule 3n + 2: each figure adds a new group of 3 tiles, and a column of 2 tiles stays the same in every figure, so 3 × 1 + 2 = 5, 3 × 2 + 2 = 8 and 3 × 3 + 2 = 11 match the counts. The video then names the 3 the coefficient, the amount added each time, and the 2 the constant, the part that never changes.

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In one sentence

The question this lesson answers

What do the two numbers in 3n plus 2 mean?

This growing pattern of tiles follows the rule 3n plus 2.

Transcript

What the lesson says

What do the two numbers in 3n plus 2 mean?

This growing pattern of tiles follows the rule 3n plus 2.

In the rule, n is the figure number.

Figure 1 has 5 tiles, Figure 2 has 8, and Figure 3 has 11.

Each new figure adds 3 more tiles.

Figure 1 has 1 group of 3, Figure 2 has 2 groups, and Figure 3 has 3 groups.

So n groups of 3 make 3 times n tiles, the 3n in the rule.

The 2 tiles on the left are the same in every figure.

They are the plus 2 in the rule.

For Figure 3, 3 times 3 is 9, and 9 plus 2 is 11.

Figures 1 and 2 match too, with 5 and 8 tiles.

The 3 is called the coefficient, the number of tiles added each time.

The 2 is called the constant, because it never changes.

So in 3n plus 2, the 3 is added each time, and the 2 stays the same.

Curriculum

Where this fits

British Columbia, Grade 7

Mathematics, Patterns and algebra: discrete linear relations, using expressions, tables, and graphsBC7-MA-39

Previous: Reading the rule from a graphNext: Equations as a balance

The outcomes and strands follow the British Columbia curriculum.

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