SOLUTION: If the sequence above continues in the same pattern, how many small triangles would be needed to make the figure that would occur in Step 5?

Question 86092: If the sequence above continues in the same pattern, how many
small triangles would be needed to make the figure that would
occur in Step 5?
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Lets represent the visual sequence as a sequence of numbers. I'm going to count the number of triangles in each term and use that as the number. For instance, the first term has one triangle, so the sequence starts with 1. The 2nd term has 4 small triangles, so the next number is 4, etc. So the sequence looks like this

1,4,9,...

Now this looks like the sequence of perfect squares. Notice that this sequence increments by an odd number each time Also notice that to go from 1 to 4, you add 3. To go from 4 to 9, add 5. So to go from 9 to ?, simply add 7 (the next odd number). Finally to go from 16 to ?, just add 9 to get 25. So the fifth step would have 25 small triangles.

So the answer is B)
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