Question 524847
First you should know what is an average:


Average = sum of the quantities divide by number quantities


Example (1)
you drink 10 glasses of water on day 1
you drink 9 glasses of water on day 2
you drink 11 glasses of water on day 3
you drink 12 glasses of water on day 4
you drink 8 glasses of water on day 5
you drink 7 glasses of water on day 6
you drink 13 glasses of water on day 7


You drink 70 glasses of water in a week (7 days)


Now what is your average of drinking water = Sum of Quantities / Number of Quantities
your average for the week will be = 70/7 = 10 glasses of water per day.


Example (2)
You save some money every month
You save in January = $20
You save in February = $15
You save in March = $11
You save in April = $09
You save in June = $18
You save in July = $20
You save in August = $22
You save in September = $23
You save in October = $15
You save in November = $17
You save in December = $10


Sum the quantities = 20+15+11+09+18+20+22+23+15+17+10 = $180
Number of quantities = 12
Average = sum of the quantities / number of quantities
Average = 180/12 = $15


So your monthly saving = $15 per month




Now come to your question
John travelled 630 km in 7 hours what was his average speed?


sum of quantities = 630 km
Number of quantities = 7 hours


Average speed = 630/7 = 90km
Means John travels 90km per hour or his average speed was 90km per hour.