Provide an appropriate response.
-A formula for the focal length of a lens is $$f = \frac { a b } { b + a }$$ Calculate f (the focal length) for a = 8 cm and b = 17 cm. Round to the nearest tenth.
A) 2.6 cm
B) 4.0 cm
C) 8.5 cm
D) 5.4 cm

Question

Quizplus · Accepted Answer

Using the formula $f = \frac{ab}{b + a}$ with $a = 8$ cm and $b = 17$ cm, we get $f = \frac{8 \times 17}{8 + 17} = \frac{136}{25} = 5.44$ cm, which rounds to 5.4 cm.

Provide an Appropriate Response f=abb+af = \frac { a b } { b + a }f=b+aab​

Provide an Appropriate Response $f = \frac { a b } { b + a }$