Answer:
can't understand the question.
Let x and y be the 2 parts of 15 ==> x + y=15 (given)
Reciprocal of x and y ==> 1/x +1/y ==> 1/x + 1/y = 3/10 (given)
Let's solve 1/x + 1/y = 3/10 . Common denominator = 10.x.y (reduce to same denominator)
==> (10y+10x)/10xy = 3xy/10xy ==> 10x+10y =3xy
But x+y = 15 , then 10x+10y =150 ==> 150=3xy and xy = 50
Now we have the sum S of the 2 parts that is S = 15 and
their Product = xy =50
Let's use the quadratic equation for S and P==> X² -SX +P =0
Or X² - 15X + 50=0, Solve for X & you will find:
The 1st part of 15 is 10 & the 2nd part is 5
Well, the first 16 were about 16*75=$1200 extra. The last 8 were $720 lost. Thus, the total profit is $480. He bought them with $7200, which means the profit is around 6.67%.
Is this question asking for descriptions?
In order to calculate, you need to find their LCM
LCM of 5,6 and 8 is equal to 120
So, That time will be 120 sec = 2 min.
In short, Your Final Answer would be 2 min.
Hope this helps!