"marco can build a laptop twice as fast as cliff. working together, it takes them 5 hours. how long would it have taken marco working alone?"

The time that it would take Marco is 7.5 hours if he is working alone.

First of we have to define a variable t as Marco's work rate.

T = Rate of Marco

Secondly we have to define Cliff's work rate as T/2. This is because Marco is two times faster than he is is. Therefore Cliff's rate is half of Marco's

We add the rate of both of them

T/2 + T = 1/5

We find the LCM

15t = 2

When we divide through by t

T = 7.5 hours

Therefore the time it would take Marco is 7.5 hours

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