How many 3digit even numbers can be formed by ,1,2,3,4,6,7 without repetition?
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Answered by
11
hello..
When unit's place is filled up both 4 or 6 again we have...
using the formula.....nPr=n!(n−r)!nPr=n!(n−r)!
Let 2 be fixed at unit's place.Now we have 5 digits and 3 places....
This can be in 5P25P2 ways.
∴ 4-digit even numbers are
3×5P2=3×5!/(5−2)!
⇒3×5!/3!
⇒3×5×4×3×2×1/3×2×1
⇒3×5×4
⇒60
thank you...
When unit's place is filled up both 4 or 6 again we have...
using the formula.....nPr=n!(n−r)!nPr=n!(n−r)!
Let 2 be fixed at unit's place.Now we have 5 digits and 3 places....
This can be in 5P25P2 ways.
∴ 4-digit even numbers are
3×5P2=3×5!/(5−2)!
⇒3×5!/3!
⇒3×5×4×3×2×1/3×2×1
⇒3×5×4
⇒60
thank you...
Answered by
1
Let the 3 digit even number be Only 3 numbers are possible at units place (2 , 4 & 6) as we need
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