A certain number of workers can finish a piece of work in 100 days. If there were 10 workers less, it would take 10 days more for the work to be finished. How many workers were there originally?
A man can row a boat at 25/9 meters per second in still water and the speed of the stream is 8 kmph. What is the
time taken (in hours) to row a distance of 90 km down the stream ?
If x is the average (arithmetic mean) of 4a and 26, y is the average of 5a and 36, and z is the average of 3a and 28, what is the average of x , y, and z in terms of a?
Since the average (arithmetic mean) of two numbers is equal to the sum of the two numbers divided by 2, the equations x= (4a+26)/2
y = (5a+36)/2 and
z = (3a+28)/2
The average of x, y, and z is given by (x+y+z)/3
Substituting the expressions in a for each variable (x, y, z) gives = ((4a+26)/2 + (5a+36)/2 + (3a+28)/2)/3 = (12a+90)/6 = 2a + 15