Engineering Board Exam Reviewer · Variation & Proportion · medium
The illumination from a lamp varies inversely as the square of the distance. At 3 m the illumination is 80 lux. What is it at 6 m?
- 20 lux
- 40 lux
- 160 lux
- 10 lux
Answer
A. 20 lux
Solution
I=k/d2 with k=80(3)2=720. At 6 m: I=720/36=20 lux.
More Variation & Proportion questions
- If 8 men can complete a job in 15 days, how many days will 12 men need to complete it?
- y varies directly as x, and y=12 when x=4. Find y when x=10.
- Find the mean proportional of 4 and 36.
- A company sells 80 units and makes P80 profit. It sells 110 units and makes P140 profit. If the profit is a linear function of the number…
- Given that w varies directly as the product of x and y and inversely as the square of z, and that w=4 when x=2, y=6, and z=3. What is the…
- If x varies directly as y and inversely as z, and x=14 when y=7 and z=2, find x when z=4 and y=16.
- Given that w varies directly as the product of x and y and inversely as the square of z, and that w=4 when x=2, y=6, and z=3, find the…
- The electrical resistance offered by an electric wire varies directly as the length and inversely as the square of the diameter of the…
- In Physics, when temperature is constant, the volume of gas is inversely proportional to the pressure. When the volume is 0.08 cu. ft, the…
- z varies jointly as x and the square root of y. If z=24 when x=3 and y=16, find z when x=5 and y=9.