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Question 15 Marks
If a figure gives a matchstick pattern of triangles. Find the general rule that gives the number of matchsticks in terms of the number of triangles.
$i.\ $
$ii.\ $
$iii.\ $
$iv.\ $
Answer


From the above figure, it can be concluded that the letter $Z$ will require $3$ matchsticks
Therefore, The pattern is $3n.$
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Question 25 Marks
Look at the following matchstick pattern of squares (Fig.). The squares are not separate. Two neighbouring squares have a common matchstick. Observe the patterns and find the rule that gives the number of matchstick in terms of the number of squares. 
(Hint : If you remove the vertical stick at the end, you will get a pattern of Cs.)



Answer
From the given figures in the question, we it can be seen that,
The number of matchsticks in the above-given pattern are $4, 7, 10$ and $13$ respectively.
$4 = 3(1) + 1,$
$7 = 3(2) + 1,$
$10 = 3(3) + 1$
$13 = 3(4) + 1$
Hence, the pattern for above-given figures will be:
$3n + 1$ where $n = 1, 2, 3, ...$ represents the number of squares.
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