Still confused by method.

800(.7) - y = (800-y).6 => 560-y=480-.6y How is y = 200?

Sub 480 from 560 = 80, add y to rhs =-.5y = 80/.5 = 160

ans is 6 & 6. Why?

if you add 6 & 6 to the list the, avg does not change and adding the two #'s will actually make the std dev smaller because you have more #'s that are less from the mean(std dev).

I'm still confused.
"One-forth of a solution that was 10 percent sugar by weight was replaced by a second solution"
I'm confused why 1/4 of the solution is not mult by 10%. Why are we mult 3/4 time the 10%.

Am I not reading the qeustion or is there a hidden trap I'm not seeing

IMHO "a new species" is referring to a single species of sparrow not the "species" or all of the "species" sparrow.

IMO C

Total sales = 40000
total cost: car 1) 20000=x(1.25) car sold for a profit of 25%
total cost: car 2) 20000=x(.8) car sold for a loss
total cost for car 1 & 2 is 41000 - told selling price of 40000 = 1000 loss

Let me know if correct & if you have any questions

IMO e)36

Whats OA?

IMO ans = .70

Day 1) .10
Day 2) is double or now .20
Day 3) double or now .40
Day 4) double or + .30 => it will be .30

Total fine = .70

Whats OA?

IMO 12. if this is correct, here's how. write 3 equations: 1)j=2f 2)s=f-2 3)j-4=4s Sub equation 1 & 2 into 3 to get 2f-4=4(f-2) & solve for f to get 2. Now this is how old f is 4 yrs ago because we solved for the 4 yrs ago equation. If f=2 4 yrs ago then f=6 now. plug that 6 into equation 1 ...