A boy rides away from home in an automobile at the rate of 28 km/h and walks back at the rate of 4 km/h. The round trip
bequires 2 hours. How far does he ride?​

7 miles

Step-by-step explanation:

Let x be the number  of hours he rides away from home at 28 mph.

Then, since the speed of the automobile is 7 times his walking speed, the number of hours he spends walking is 7x.

Then, the total time, which is 2 hours, is equal to x plus 7x, or 8x.

8x=2-->x=1/4

So the amount of time he spends in the automobile is x=1/4 hour.

The distance he travels in 1/4 hour at 28 mph is 7 miles.

Avg speed of the round trip= 2*28*4/(28+4)= 7 mi/hr

RT=7*2=14 miles

--> 7 miles each way.

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.

12

step-by-step explanation:

12 + 5 = 17

12x2=24

24-7=17