Question

Use the digits 1, 2, 3 and 4 only once to form two 2-digit numbers so that the sum will be 55? *​

Answer 1

Answer:

Solution

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Correct option is A)

First find the number of 5 digit numbers which has 5 at unit's place.

When 5 is at unit's place, the remaining 4 places can be filled by 2,3,4,4 in

2!

4!

=12

Similarly when 4,3 and 2 are at unit's place we get 24,12,12 five digit numbers respectively.

So when we add all such numbers obtained the total sum of units' place digits will be 12(5+3+2)+24×4=216.

Same pattern will follow for other places as well.

Hence, the total sum=(10

4

+10

3

+10

2

+10+1)216=2399976

Answer 2

4+1=5

2+3=5

55

this is the answer