Every train carriage has 4 doors how many doors will the train have if there are 7 carriages

28

Step-by-step explanation:

4*7=28

First write down the unit ratio that is involved.

In this case, it's train carriage/doors.

Next, we set up our proportion.

We know that for every train carriage, there are 4 doors.

So we have 1/4.

We are asked how many doors will there be is there are 7 carriages.

So we have 7/x.

The 7 must go on the top because our unit ratio says

that we must put train carriage/doors.

So we have 1/4 = 7/x.

Solving from here, we use the means-extremes property.

This states that the product of the extremes, (1)(x),

equals the product of the means, (4)(7).

So we have 1x = 28 or just x = 28.

This means that for 7 carriages, there are 28 doors.

∞ this is your sign

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.