Hi
Alex75PAris,
Its just the rate which is different for older machines and New machine. However, as I see from your equations you have changed the time as well.
Further, you have taken 2 variable for 2 machines Ra and Rb, if you are already multiplying the rate of new machine by 2 then you don't need to take 2 variables.
The more you take variables in a question, more difficult it would be to crack
Simple eauation will be
Work = Rate x Time
For old machines-
1= R x T
T= 1/R (This is the combined rate of two old machines)
For new machine (Single machine)-
1= 2R x T
T= 1/2R
(1) Each of the older machines, working alone at its constant rate, can fill half a production order in less than 4 hours.
If 1 old machine take less than 4 hour to complete HALF a PRUDUCTION
the to complete a FULL production it will take less than 8 hours
If 1 machine take less than 8 hours to complete FULL production in less than 8 hours
than 2 machine will take less than 4 hours to complete
So, the new machine will take less than 2 hour to complete FUll production (because its rate is double from two pld machines)
For, easy understanding lets remove less than and treat this question as 4 hours and 2 hours
Means- Two old machine take = 4 hrs to complete a work
New machine take = 2 hours to complete a work
So, working together all three machines can complete a work in
(1/4) + (1/2) = 1/R
R= 4/3
SO, Time taken to complete a work will be 3/4= 0.75 hours
Remember we replace LESS THAN with equal time
We can cay that to complete a work both will take ATLEAST 0.75 hours weather it will be actually more than 1 hr, WE ARE NOT SURE.
So, statement 1 is inufficient
_________________
Thanks and Regards,
Prakhar