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Question
primary 6 | Maths
| Geometry
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Help Radhika! Anyone can contribute an answer, even non-tutors.
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Date Posted: 3 years ago
Views: 194
Number of black triangles in a particular figure
= ½ x (Figure number) x (Figure number + 1)
Eg.
Figure 1
½ x 1 x 2 = ½ x 2 = 1
Figure 2
½ x 2 x 3 = ½ x 6 = 3
Figure 3
½ x 3 x 4 = ½ x 12 = 6
Figure 4
½ x 4 x 5 = ½ x 20 = 10
So for Figure 40, number of black triangles
= ½ x 40 x 41
= 820
Number of matchsticks
= 3 x number of black triangles
= 3 x 820
= 2460
Do the same method for the next part
= ½ x (Figure number) x (Figure number + 1)
Eg.
Figure 1
½ x 1 x 2 = ½ x 2 = 1
Figure 2
½ x 2 x 3 = ½ x 6 = 3
Figure 3
½ x 3 x 4 = ½ x 12 = 6
Figure 4
½ x 4 x 5 = ½ x 20 = 10
So for Figure 40, number of black triangles
= ½ x 40 x 41
= 820
Number of matchsticks
= 3 x number of black triangles
= 3 x 820
= 2460
Do the same method for the next part
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