もう vs もっと

[Fociis]

Can someone tell me the difference between the two and when to use each one? Its rather confusing to me.

 

[PaulTB]

Can someone tell me the difference between the two and when to use each one? Its rather confusing to me.

もう already
もう again/more
もっと more
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ケーキもたべてください。
Please eat some cake as well.
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ケーキをもっとたべてください。
Please eat some more cake.
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ケーキはもうたべました。
I've already eaten the cake.
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もう一回やってみてください。 ○
Please try one more time.
もっと一回やってみてください。× ← Can't say this.
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もう１０分すれば終えるでしょう。
Another 10 minutes and we'll probably be able to finish it.
もっと１０分すれば終えるでしょう。× <- can't say this
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I think that when used for 'more/again' もう is used before a unit of time or 'times'.