The figure shows a pattern formed using some rods.
- How many rods are needed to form 18 triangles?
- How many triangles are formed using 207 rods?
1 triangle = 1 + (2 x 1) = 3 rods
2 triangles = 1 + (2 x 2) = 5 rods
3 triangles = 1 + (2 x 3) = 7 rods
Formula Number of rods = 1 + (2 x Number of triangles)
(a)
18 triangles
= 1 + 2 x 18
= 37 sticks
(b)
1 + (2 x Number of triangles) = 207 rods
2 x Number of triangles = 207 - 1 = 206 rods
Number of triangles = 206 ÷ 2 = 103
Answer(s): (a) 37; (b) 103
