MGMAT tough ratio sum

[vkb16]

as the pic, OA after a few replies

the solution says it ''assumes'' that the faster machine does 2 of the 3 loads. What the hell? how? and why??

[DeepakR]

Average dryer takes 80 minutes for 1 full load

Given that, Ratio of the speed of Super/Ratio of speed of Average dryer = 5/4

i.e If S takes 4 minutes to complete A will take 5 minute on average.

If A takes 80 mins for 1Load
Hence S will take 64 mins for 1 load. For 3 loads S will take 64 * 3= 192 minutes.

So if he is starting the load in both the dryers

In the 64th min - S will complete the 1st load and will proceed with the 2nd load and complete the 3rd load at 128th minute.

In the mean time A will do the 2nd load at the 80th minute.

Hence total time = 64+80+64= 208 mins. I am not sure if this correct.

-Deepak

[maihuna]

speed of avg mc = 80 minute per round
faster mc = (80/5)*4 = 64 minute per round

there are three lots: by faster mc it will take: 64*3 = 192 minutes

Combined average : 1/64 + 1/80 = (5+4)/16*4*5 = 9/16*4*5

One lot will take : 16*4*5/9
3 lot will take : 3*16*4*5/9 = 320/3 = 106.66 minutes.

[dumb.doofus]

I dont think there is any need to find average or anything.. just sequential loading of machine is enough for us to determine the total time..

Of course we need to use the faster machine twice coz it does the job faster for us..

ok. steps:

1. Time taken by Average machine per load = 80 mins
ratio is 5:4 so,
2. Time taken by faster machine per load = 64 mins..

so the total time taken would be twice the time for the faster machine i.e. 128 mins.. that's it.. coz in that time, the slower machine would finish one round of laundry..

so answer is 128 mins and that's the total time

[DeepakR]

Dumb doofus I thought that the question had asked for the total time taken by both the machines together. I couldn't interpret it as time taken only by S alone. Am I missing something ? I would be happy if someone/you can help me here.

-Deepak

[vkb16]

hi.. heres the solution as given in the text...

thanks for the explantion dumb.doofus, I only had that part to clear out

thanks all

[cramya]

The question may be there for people to decipher the 5:4 ratio part

5 parts is 80
4 parts will be 64

Good solution, Dumb.Doofus.

Regards,
CR