Question

The surface area of a cone is given by the formula S = πl + πr2. Solve the formula for l.

A) l = S – r2
B) l = S + r2
C) l = 5/3.14 – r2
D) l = 5/3.14 + r2

all of the 2's are to the power of R
the 5/3.14's are fractions

Answer 1

l = S/π - r^2 .......
.......

Answer 2

If the surface area of a cone is given by the formula
`S=\pi\cdot l+\pi\cdot r^2,` then you have to express l in terms of S and r.

1. Express the whole expression
`\pi\cdot l:`

`\pi\cdot l=S-\pi\cdot r^2.`

2. Divide the previous expression by
`\pi:`

`l=(S-\pi r^2)/(\pi)=(S)/(\pi)-r^2.`

3. Since
`\pi\approx 3.14,` then

`l=(S)/(3.14)-r^2.`

Answer: correct choice is C (here should be S not 5 as written)