A cone has radius 3 and height 4. Your classmate calculates its surface area as shown:

Mathematics

1 answer:

I am Lyosha [343]3 years ago

4 0

Answer:

Lateral surface area of cone = π(3)(5)

Lateral surface area of cone = 47.1 unit² (Approx.)

Step-by-step explanation:

Given:

Radius of cone = 3 unit

Height of cone = 4 unit

Find:

Lateral surface area of cone

Computation:

Slant height of cone = √Radius² + Height²

Slant height of cone = √3² + 4²

Slant height of cone = √9 + 16

Slant height of cone = √25

Slant height of cone = 5 unit

Lateral surface area of cone = πrl

Lateral surface area of cone = π(3)(5)

Lateral surface area of cone = (3.14)(15)

Lateral surface area of cone = 47.1 unit² (Approx.)

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We need to find an equation for each situation. Let x be the number of GB of data used.

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$30+5x=50+2x \\ Subtracting \; 2x \; \& \;30\; on\; both\; sides\; \\ \\30+5x-2x-30=50-30+2x-2x \\Combining \; like \; terms\\\\3x=20\\Dividing \; like \; terms\\\\ \frac{3x}{3}=\frac{20}{3} \\ \\x=6\frac{2}{3}$

When

$x=6 \\\\ Plan \; A \; Cost = 30+5(6)=30+30=\$60\\ Plan \; B \; Cost = 50+2(6)=50+12= \$72\\ \\ From \; 5\leq x\leq 6\frac{2}{3} , \; Plan \; A \; is \; Cheaper!$

When

$x = 7\\\\ Plan \; A \; Cost= 30 + 5(7) =30+35 = \$65\\\\Plan \; B \; Cost = 50 + 2(7)=50+14=\$64 \\ \\ From \; 6\frac{2}{3} \leq x \leq 8, \; Plan\; B \; is \; Cheaper !$