Answer:
-7
Step-by-step explanation:
You use the quadratic formula of to get:
a = 1
b = 7
c = -13
then you plug that into x= (-b ± √b²-4ac)/(2a) :
x= ( -7 ± √7²- 4(1)(-13) )/(2(1))
The sum of these two x values turns out to be:
Answer:
3
Step-by-step explanation:
If 30% were perfect, 70% were not perfect. So we know that 70% of the total number of photographs is 210.
p(70/100)=210 multiply both sides by 100
70p=21000 divide both sides by 70
p=300
So there are 300 photographs in all.
Answer:
Lucy had 40 books last year.
Step-by-step explanation:
assuming 100% is the percent;
100% + 70%
100 : x
170 : 68
cross multiply = 170x = 100 x 68
-------- ————-
170 170
cancel 170/170
therefore x = 100 x 68 divided by 170
result is 40
Answer:
(I suppose that we want to find the probability of first randomly drawing a red checker and after that randomly drawing a black checker)
We know that we have:
12 red checkers
12 black checkers.
A total of 24 checkers.
All of them are in a bag, and all of them have the same probability of being drawn.
Then the probability of randomly drawing a red checkers is equal to the quotient between the number of red checkers (12) and the total number of checkers (24)
p = 12/24 = 1/2
And the probability of now drawing a black checkers is calculated in the same way, as the quotient between the number of black checkers (12) and the total number of checkers (23 this time, because we have already drawn one)
q = 12/23
The joint probability is equal to the product between the two individual probabilities:
P = p*q = (1/2)*(12/23) = 0.261
T