The Triangles and Its Properties — MATHS STD 7 — Question
Gujarat BoardEnglish MediumSTD 7MATHSThe Triangles and Its Properties2 Marks
Question
Find the perimeter of the rectangle whose length is $40 \ cm$ and a diagonal is $41 \ cm.$
✓
Answer
Breadth of the rectangle can be calculated by using Pythagoras rule because length, breadth and diagonal would make a right-angled triangle.
$\text { So, } h^2=p^2+b^2$
$\Rightarrow 41^2=40^2+b^2$
$\Rightarrow 1681=1600+b^2$
$\Rightarrow b^2=1681-1600=81$
$\Rightarrow b^2=9 \times 9$
$\Rightarrow b=9 \mathrm{~cm}$
Perimeter can be calculated as follows:
$\text { Perimeter }=2 \text { (length }+ \text { breadth })$
$=2(40+9)=2 \times 49=98 \mathrm{~cm}$
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