Question

The area of a telescope lens is 7903 rnrn2 {a) What is the area in square feet (ft2)? (b) If it takes a technician 45 s to polish 135 rnm2, how long does it take her to polish the entire lens?

Answer 1

Answer:

Area is 0.08504$ft^{2}$ and $2.6\times 10^{3}s$ are needed for polishing

Explanation:

(a) ft is unit of F.P.S system whether mm is unit of M.K.S system.

According to unit conversion, $1mm=0.00328ft$

So, $1mm^{2}=(0.00328)^{2}ft^{2}=1.076\times 10^{-5}ft^{2}$

hence, $7903mm^{2}=7903\times 1.076\times 10^{-5}ft^{2}=0.08504ft^{2}$

So, area of telescope lens is 0.08504$ft^{2}$

(b)$135mm^{2}$ are polished in 45s

So, $7903mm^{2}$ are polished in $\frac{45\times 7903}{135}s$ or $2.6\times 10^{3}s$