The figure shows a pattern formed using some straws.
- How many straws are needed to form 19 triangles?
- How many triangles are formed using 193 straws?
1 triangle = 1 + (2 x 1) = 3 straws
2 triangles = 1 + (2 x 2) = 5 straws
3 triangles = 1 + (2 x 3) = 7 straws
Formula Number of straws = 1 + (2 x Number of triangles)
(a)
19 triangles
= 1 + 2 x 19
= 39 sticks
(b)
1 + (2 x Number of triangles) = 193 straws
2 x Number of triangles = 193 - 1 = 192 straws
Number of triangles = 192 ÷ 2 = 96
Answer(s): (a) 39; (b) 96
