I'm pretty sure the answer is 4 because, 4*21= 84.
First. y=2x
second d is correct
third is a
Using a calculator or a pencil, find each square root, including
three (3) decimal places. A negative number has no real square
roots, so skip '-71' and '-19'.
For each square root . . .
-- If the digits in the 2nd and 3rd decimal place are 00 through 24, then
make the 2nd decimal place a '0' and discard the rest.
-- If the digits in the 2nd and 3rd decimal place are 25 through 74, then
make the 2nd decimal place a '5' and discard the rest.
-- If the digits in the 2nd and 3rd decimal place are 75 through 99, then
increase the 1st decimal place by 1, make the 2nd decimal place a '0',
and discard the rest.
There are 6! = 720 ways of arranging the lamps.
If the leftmost lamp is red, there are 3 choices of lamp in the leftmost position, and the remaining 5 can be placed in any order, so there are 3×5! = 360 ways of arranging the lamps and the leftmost is red.
Hence there is a 360/720 = 1/2 probability that the leftmost lamp is red.
Ignoring lamp color for the moment, the probability of arranging 3 lit lamps and 3 unlit lamps is the same, 1/2.
Since Ryan arranges the lamps randomly by color, then turns 3 of them on randomly, the two events are independent. So
P(leftmost red AND leftmost lit) = P(red) × P(lit) = 1/2² = 1/4
