Answer:
2 pieces
Step-by-step explanation:
Given


Required
Calculate the number of pieces
To do this, we have to divide the length of the wood by the length of each piece.
Represent this with x


Convert mixed numbers to improper fraction

Change division to multiplication



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1 x 9, 3 x 3, 9 x 1
1 and 9 are a factor pair of 9 since 1 x 9= 9
3 and 3 are a factor pair of 9 since 3 x 3= 9
9 and 1 are a factor pair of 9 since 9 x 1= 9
Triangle ABC is congruent to triangle MNC by SSS, AAA or AA .....!!
We have similar triangles so
12/x = (12+78)/(x+13)
We can skip some algebra by doing the ratio on the pieces. We'll show it works at the end.
12/x = 78/13
x = 12(13)/78 = 2
We check
12/2 = 6
(12+78)/(2+13) = 90/15 = 6, good
Answer: x=2