You're trying to find constants
such that
. Equivalently, you're looking for the least-square solution to the following matrix equation.
To solve
, multiply both sides by the transpose of
, which introduces an invertible square matrix on the LHS.
Computing this, you'd find that
which means the first choice is correct.
I tried to make a list and found 27 ways
tell me if I missed any
order is
(3point,2point,1point)
(0,0,15)
(0,1,13)
(0,2,11)
(0,3,9)
(0,4,7)
(0,5,5)
(0,6,3)
(0,7,1)
(1,0,12)
(1,1,10)
(1,2,8)
(1,3,6)
(1,4,4)
(1,5,2)
(1,6,0)
(2,0,9)
(2,1,7)
(2,2,5)
(2,3,3)
(2,4,1)
(3,0,6)
(3,1,4)
(3,2,2)
(3,3,0)
(4,0,3)
(4,1,1)
(5,0,0)
27 is my answer
600×3.5%=21. As a result, there are 21 phones that likely to be defective. Hope it help!
There are two methods that can be used to write 0.368 in expanded form.
Method-1:
Take the first number after the decimal point and divide it by 10. Take the second number after the decimal point and divide it by 100. Take the third number after the decimal point and divide it by 1000. Lastly, add all of them.
Method-2:
Multiply first number after decimal point with 0.1; multiply second number after decimal point with 0.01; multiply third number after decimal point with 0.001, and add them all.
(3 * 0.1) + (6 * 0.01) + (8 * 0.001) = 0.368
