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One model of a portable keyboard, Model A, has a total of 61 black and white keys. It has five full octaves with 5 black keys in each octave. The Model B portable keyboard has 76 black and white keys. It has six full octaves with 5 black keys in each octave and one extra black key.

Find the number of white keys on the Model A keyboard.

Find the number of white keys on the Model B keyboard.

use this formula:

p(a\b) = p(a and b)/p(b).

take it from here.

(d)

step-by-step explanation:

given: the line in the graph passes through points (5,30) and (6,26).

then, the equation of line is:

now, put y=a(n) and x=n,

hence, option d is correct.

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.