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.
Answer:Let the base of the 15ft long ladder be placed x ft away from the wall so that it exactly reaches the top of a 12- foot tall wall.
By Pythagorean theorem
12
2
+
x
2
=
15
2
⇒
x
2
=
15
2
−
12
2
=
81
⇒
x
=
√
81
=
9
ft
Step-by-step explanation:
Answer:
40%
Step-by-step explanation:
20 out of 50 simplifies to 2 out of 5 which is equivalent to 4 out of 10 which is also 40 out of 100 which is 40%.
X (unknown number at first is 28) is the number 28.
28/7=4. 2(28) divided by 7= is also 56 divided by 7.
Which is 8. 8 is the final answer.
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