Ratio and Proportion

[karishma315]

Please explain ow to solve tese questions:

1). It takes the average dryer 80 minutes to dry one full load of Bobs laundary . Bob has one average dryer and also decides to try one jumbo dryer faster than average by ratio of 5:4. Bob as three loads of laundary and both machines are so precise that he can set them to minute. how many minutes does it take for him to dry his three loads?( Assume tat no time passes btw loads and that he can use both machines concurrently.Assume that he never runs a machine with less than full load. finally assume that Bob does not partially dry a load in one machine and then switch it to the other.)

Eagerly looking for a response. Thanks in advance.

Regards
Karishma

[GMATGuruNY]

It takes the average dryer 80 minutes to dry one full load of Bob's laundry. Bob has one average dryer, and also decides to try one "Super Jumbo-Iron Dryer-Matic", which is faster than the average dryer by a ratio of 5 : 4. Bob has three loads of laundry, and both machines are so precise that he can set them to the minute. How many minutes does it take for him to dry his three loads? (Assume that no time passes between loads and that he can use both machines concurrently. Assume also that he never runs a machine with less than a full load. Finally, assume that Bob does not partially dry a load in one machine and then switch it to the other.)

Since the rate ratio = 5:4, let the rate of the fast machine = 5 units per minute and the rate of the slow machine = 4 units per minute.
Since the slow machine completes one load in 80 minutes, one load = r*t = 4*80 = 320 units.
Time for the fast machine to complete 320 units = w/r = 320/5 = 64 minutes.
Thus, the fast machine can complete 2 loads in 128 minutes -- more than enough time for the slow machine to complete 1 load.
Thus, the 3 loads will be completed in 128 minutes.

[OptimusPrep]

Please explain ow to solve tese questions:

1). It takes the average dryer 80 minutes to dry one full load of Bobs laundary . Bob has one average dryer and also decides to try one jumbo dryer faster than average by ratio of 5:4. Bob as three loads of laundary and both machines are so precise that he can set them to minute. how many minutes does it take for him to dry his three loads?( Assume tat no time passes btw loads and that he can use both machines concurrently.Assume that he never runs a machine with less than full load. finally assume that Bob does not partially dry a load in one machine and then switch it to the other.)

Eagerly looking for a response. Thanks in advance.

Regards
Karishma

The best way to solve these questions is to start noting down the information to see a clear picture.

Time taken by average dryer = 80 minutes
Time taken by super jumbo dryer = 4/5*80 = 64 minutes.

The fastest way to complete the loads is not use machines simultaneously
Hence 2 loads in super dryer and 1 load in the average dryer.

Time taken for 2 loads = 64*2 = 128 minutes.
In this time, the average dryer will also complete one load.

Total time taken for 3 loads = 128 minutes.

You should keep in mind here that the dryer if stuffed with 1 cloth will take the same time as a dryer stuffed with 10 clothes.