Question

24. The figure shows the cross-section of the interior part of a
thermos flask.
The top part is a trapezium, the middle part is a rectangle
and the bottom part is a semi-circle.
If CE = 20 cm, BC = 25 cm, AB = GF = 13 cm, AG = 10 cm
and AN = 12 cm, the find:
(1) The perimeter of the cross-section
(ii) The area of the cross-section
20
С
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E​

Answer 1

Perimeter of the cross section = 120.4 cm

Area of the cross section = 837 cm²  

Solution:

Given CE = 20 cm, BC = 25 cm,

AB = GF = 13 cm

AG = 10 cm, AN = 12 cm

Radius of the semi-circle = 20 ÷ 2 = 10 cm

Perimeter of CE = πr

                          = 3.14 × 10

                          = 31.4 cm

Perimeter of the cross section = AB + BC + CE + EF + FG + GA

                                                  = 13 cm + 25 cm + 31.4 + 25 + 13 + 13

                                                  = 120.4 cm

Perimeter of the cross section = 120.4 cm

Formulas:

Area of the trapezium =  $\frac{1}{2} \times \text{sum of the parallel side}\times\text { height}$                            

Area of the rectangle = length × width

Area of the semi-circle = $\frac{1}{2} \times \pi r^{2}$

Area of the cross section = Area of the trapezium + Area of the rectangle

                                             + Area of the semi-circle

                                         $=\frac{1}{2}\times(10+20)12+(25\times20 )+\left(\frac{1}{2}\times3.14\times10\right)$

                                         = 180 cm² + 500 cm² + 157 cm²

                                         = 837 cm²

Area of the cross section = 837 cm²  

To learn more...

https://brainly.in/question/15199084

Answer 2

Answer:

Don't know the answer of the 1st one. But the 2nd one is

$10(5\pi + 68) {cm}^{3}$