The amount of time a certain brand of light bulb lasts is normally distribued with a mean of 900 hours and a standard deviation of 35 hours. Out of 305 freshly installed light bulbs in a new large building, how many would be expected to last between 870 hours and 950 hours, to the nearest whole number?

answer: (-8,4) are the coordinates of a

step-by-step explanation:

let the side of square abcd is x .

thus the area of square abcd is .

now, by the diagram area of triangle ead= 1/2 × ea × ad = 1/2 × ea × x

( because ad is the side of square)

and, according to the question,

the areas of square abcd and right ead are equal.

⇒

⇒ea=2x

thus, ea: ab=2: 1

therefore, point a divides line segment eb into the ratio 2: 1.

⇒ by sectional formula coordinates of a are,

=

=

=(-8, 4)

thus the coordinates of a are (-8,4)

the anwser is x< -17/2