Question

find the area of a triangle two sides of sides of which are 18cm 10cm and the perimeter is 42
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Answer 1

Answer:

$let \: third \: side \: be \: x \\ x + 18 + 10 = 42 \\ x + 28 = 42 \\ x = 42 - 28 \\ x = 14. \\ semiperimeter = \frac{a + b + c}{2} \\ = \frac{42}{2} \\ = 21 \\ area = \sqrt{21 \times 3 \times 11 \times 7 } \\ = 69.64cm {}^{2} \\ = 70 {cm}^{2} .$