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find the surface area of the following.


1. S= 25cm

formula: SA= 6s 2

a) 3.750cm2
b) 3.625cm2
c) 2.750cm2
d) 1.150cm2

2. l = 16cm , w = 9cm, h = 8cm

formula: SA= 2 (lw + lh + wh).

a) 900cm2
b) 688cm2
c) 588cm2
d) 480cm2

3. d= 14cm, h = 23cm

formula: SA = 2πr2 + 2πrh

a) 318.6cm2
b) 918.8cm2
c) 1, 318.8cm2
d) 2, 100.7cm2​


Sagot :

Surface Area

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1. Box

s = 25cm

Formula: [tex]\large \sf \green{SA=6s^2}[/tex]

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[tex]\big \begin{aligned} \sf SA&=\sf 6s^2 \\ \sf SA&=\sf 6(25cm)^2 \\ \sf SA&=\sf 6 \times 625cm^2 \\ \sf SA&= \boxed{\bold{\purple{\Large 3750 \ cm^2}}} \end{aligned}[/tex]

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2. Rectangular Prism

l = 16cm , w = 9cm, h = 8cm

Formula: [tex]\large \sf \green{SA=2(lw+lh+wh)}[/tex]

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[tex]\big \begin{aligned} \sf SA&=\sf 2(lw+lh+wh) \\ \sf SA&=\sf 2(16cm \times 9cm+16cm \times 8cm+9cm \times 8cm) \\ \sf SA&=\sf 2(144cm^2+128cm^2+72cm^2) \\ \sf SA&=\sf 2 \times 344cm^2 \\ \sf SA&= \boxed{\bold{\purple{\Large 688 \ cm^2}}} \end{aligned}[/tex]

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3. Cylinder

d = 14cm, h = 23cm

Formula: [tex]\large \sf \green{SA=2\pi r^2+2πrh}[/tex]

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[tex]\big \begin{aligned} \sf SA&=\sf 2\pi r^2+2πrh \\ \sf SA&=\sf 2 \times 3.14(7cm)^2+2 \times 3.14(7cm \times 23cm) \\ \sf SA&=\sf 6.28 \times 49cm^2+6.28 \times 161cm^2 \\ \sf SA&=\sf 307.72cm^2+1011.08cm^2 \\ \sf SA&= \boxed{\bold{\purple{\Large 1318.8 \ cm^2}}} \end{aligned}[/tex]

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