QQuestionMathematics
QuestionMathematics
How many triangles are there?
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Answer
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Step 1:: Identify the number of triangles in the figure.
In the given figure, there are 7 rows of triangles. The first row contains 1 triangle, the second row contains 2 triangles, and so on. The number of triangles in each row follows an arithmetic sequence with an initial term (a) of 1, a common difference (d) of 1, and the number of terms (n) being the position of the row.
Step 2:: Calculate the number of triangles in the last row.
T_7 = 1 + (7-1) \times 1 = 1 + 6 \times 1 = 1 + 6 = 7
The last row is the 7th row, so we need to find the number of triangles in the 7th row. To do this, we use the formula for the nth term of an arithmetic sequence: Where: - Tn is the nth term - a is the initial term - n is the position of the term - d is the common difference For the 7th row: So, there are 7 triangles in the last row.
Step 3:: Calculate the total number of triangles.
Sum = \frac{7}{2} (1 + 7) = \frac{7}{2} \times 8 = 28
To find the total number of triangles, we can sum up the number of triangles in each row: This is the sum of an arithmetic series with n = 7. We can use the formula for the sum of an arithmetic series: Where: - Sum is the sum of the series - n is the number of terms - a is the first term - l is the last term For our problem:
Step 4::
Final Answer
There are 28 triangles in the figure.
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