~ ANSWER=1/2 ~
Simple probability is found by counting all the results which fit requirements and dividing by all possible results.
To find probability of two results in a row, multiply chance of first result by chance of second result.
Since you are replacing the marble before the second draw, we don’t have to figure out the various changes in odds for the different possible first draws. It’s just that simple.
There are 5 white marbles
There are 4 red marbles
There are always 20 marbles in all
5/20*4/20=1/4*1/5=1/20 or 1/2
By coincidence, the same as the chance of drawing the white marble in one draw.
Please tell me what’s the question. So I can answer.
So average=(total of scores)/(number of tests)
needs at least average of 70
at least is represented as greater than or equal to or the sign (<u>></u>)
70<u>></u>(total)/(number oftests)
since we have 3 tests, we have to have 3 scores so
70<u>></u>(x+y+z)/3
he scored 85 and 60
70<u>></u>(x+85+60)/3 (doesn't matter which to subsitute)
70<u>></u>(x+145)/3
multiply obht sides by 3
210<u>></u>x+145
subtract 145 from both sides
65<u>></u>x
he needs to get at leas 65 on his third test
4(4)+ 2(-5) = 6
16+ (-10) = 6
