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I having trouble with bii) finding the surface area. The answer is 2430 cm^2, but I got 2135.2 cm^2 for my total surface area. The area of cross-sectional is 148.7 cm^2. The given length for the shape is 30 cm. Below is my working
Area of side 15 + area of side 21 + area of side 13 + area of top and area of bottom + area of semi-cylinder(base + curved):
(15*30) + (21*30) + (13*30) + (2*148.7) + pi*(3.5)^2 + pi*3.5*30 = 2135.2 cm^2
Date Posted: 3 years ago
Views: 258
Why is there even a π x (3.5)² in the working? What is that for?
Surface Area formulae for cylinder I suppose: 2*pi*r^2 + 2*pi*r*l since it is semi-cylinder so it is reduced by 0.5...
But this half cylinder has already been cut out. So the two semi-circle base areas are not there. You cannot include it.
The answer should be 2097.26.
It is given as 2430 as they have included the curved surface area of the whole cylinder instead of only half.
Adding 2097.26 to this extra half :
2097.26 + π x 3.5 x 30
≈ 2097.26 + 329.87
= 2427.13
= 2430 (3s.f)
Which matches the given answer (though it's incorrect)
The answer should be 2097.26.
It is given as 2430 as they have included the curved surface area of the whole cylinder instead of only half.
Adding 2097.26 to this extra half :
2097.26 + π x 3.5 x 30
≈ 2097.26 + 329.87
= 2427.13
= 2430 (3s.f)
Which matches the given answer (though it's incorrect)
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