Answer:
72 boys=72:40
45 girls=81:45
90 girls=162:90
40 girls=72:40
etc.
Step-by-step explanation:
think of it as fractions
There are 10 chips altogether. 4 of them are white.
4/10 is the chance of lifting out a white chip
There are 3 of them left and 9 chips altogehter.
4/10 * 3/9
12/90
4/30
2/15
Comment
(my edit) it is not that 2/15 is wrong (although it is not entirely right).
1/3 is the correct answer if you assume that what happened during the first draw has nothing to do with what will happen on the second. It is like saying if you throw 11 heads in a row with a fair coin, what are the chances of throwing a heads on the 12th throw? The answer is 1/2. That is the same kind of question you have asked.
The two of us who have responded have really responded to what are the chances of drawing 2 white chips. The question really does not restrict us in a way that prevents us from saying that. I'll stick with
B <<<< answer
but I think it would be nice if the writer of the question made it clear that 1/3 should be the proper answer. I am glad you came back and posted the right answer. It makes me think.
The semi right answer is B <<<<----
If my reasoning bothers anybody, I'll reedit again. I'm only leaving it because sometimes a mistake is more instructive than a given answer.
Minimum: 1
Q1: 2.5
Q2: 5
Q3: 7
Maximum: 13
Answer:
2.4 hours
Step-by-step explanation:
Let total work = X
Rate of work done = X ÷ time
Rate of A = X/4
Rate of B = X/6
If they work together, rate is the sum of their individual rates, i.e.
X/4 + X/6
= (3X + 2X)/12 (taking LCM)
=5X/12
Rate = X/time
5X/12 = X/time
time = X÷(5X/12)
time = X × 12/(5X)
time = 2.4 hours
Shortcut:
Product of individual times/sum of individual times
= (4×6)/(4+6)
=24/10
=2.4 hours
