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The cross section section of a uniform prism is a right-angl...

The cross section section of a uniform prism is a right-angled triangle with sides 3cm. 4cm and 5cm. If its length is 10cm. Calculate the total surface area

A.

142cm2

B.

132cm2

C.

122cm2

D.

112cm2

Correct answer is B

A prism has 3 rectangular faces and 2 triangular faces and 2 rectangular faces = 10(3 + 4 + 5) = 120

Area of triangular faces = s(sa)(sb)(sc)

where s = a+b+c2

= 3+4+52

= 122

= 6

Area of = 6(630(64)(65)

= 6×3×2×1 = 6

Area of triangle faces = 2 x 6 = 12cm2

Total surface area = Area of rectangular face + Area of = 120 + 12

= 132cm2