# How many numbers can be formed? [closed]

How many numbers can be formed from 1, 2, 3, 4, 5, ( without repetition), when the digit at the unit's place must be greater than that in the ten's place?

## closed as off-topic by jvdhooft, Théophile, M. Winter, Leucippus, ShaileshJun 19 '18 at 0:31

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• Please have a look at how to ask a good question. – Théophile Jun 18 '18 at 22:25
• You can explicitly count this yourself on paper. If there are too many, you can try with $1,2,3,4$ or $1,2,3$ and see if you notice a pattern... – Jair Taylor Jun 18 '18 at 22:35

total methods without any restriction $= 5\cdot4\cdot3\cdot2\cdot1 = 120$
Ex$:$ $12$ & $21$ only one will be valid so answer will be $\dfrac{120}{2} = 60$
So, $60$ numbers can be formed using all of $1,2,3,4,5($without repetition$),$when the digit at the units place must be greater than that in the tenth place.