Which expression uses the distributive property to represent the sum of 28+42
2 answers:
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Answer: b) 6
Step-by-step explanation:
Given : The illuminance of a surface varies inversely with the square of its distance from the light source.
i.e. for d distance and l luminance , we have
, where k is constant. (1)
If the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters.
From (1), we have
(2)
For the distance (d) corresponds to the illuminance to 30 lumens per square meter , we have
Put value of k , we get
Then , the number of meters should the distance of the surface from the source be increased= 12 meters- 6 meters = 6 meters.