rates and formulae.

[ildude02]

A's rate is twice that of B and 1/3 that of C. They all combined to produce 2700 units, how many units did C produce?

a)300
b)600
c)900
d)1200
e)1800

My question is, I always get confused when to sum them all up and equate to the total and when we should use the formulae; 1/A +1/B +1/C = 1/T; where T is the total time, and then you derive the units based off the individual time. Can someone clarify this for me? Thanks!

[raunekk]

IMO:E (1800)

IF you are given total time taken to do a job by a person or a machine,

then you need to use the formula 1/a+1/b.This will give you work done per-hour by each machine individually.That is, rate.

But if u are directly given time or rate/hour of each component you dont need to use that formula..you can directly use w=rt.

This is what you are asking rite??

[ildude02]

So you just add them up to get 9x and find x instead of using the formula?

Also, isn't there a formuale for even units along with time?

Units of A/TimeA + Unites B/TimeB = Total Units/TotalTime; when do we use this formulae? If we are given indivdual times and units produced by each of them and asked to find the missing units?

Appreciate your response.

[sudhir3127]

answer is E 1800..

A+A/2+3A= 2700

A=600
hence C= 1800