Question

Find the sum of all possible 3- digits numbers which can be formed by the digits 4,6 and 8 where the repetition of the digits is not allowed ?

Answer 1

MATHS

How many 3-digit numbers can be formed from the digits 1,2,3,4 and 5 assuming that.

i) Repetition of the digits is allowed?

ii) Repetition of the digits is not allowed?

November 22, 2019avatar

Sherry Sao

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VIDEO EXPLANATION

ANSWER

1)

A three digit number is to be formed from given 5 digits 1,2,3,4,5.

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HTO

Now, there are 5 ways to fill ones place.

Since, repetition is allowed , so tens place can also be filled by 5 ways.

Similarly,hundreds place can also be filled by 5 ways.

So, number of ways in which three digit numbers can be formed from the given digits is 5×5×5=125

Alternative Method:

There will be as many way ways as there are ways of filling 3 vacant places in succession by the given five digits. In this case, repetition of digits is allowed. Therefore, the units place can be filed by any of the given 5 digits.

Similarly, tens and hundreds digits can be filled in by any given 5 digits.

Thus, by the multiplication principle, the number of ways in which three digit numbers can be formed from the given digits is 5×5×5=125

ii) A three digit number is to be formed from given 5 digits 1,2,3,4,5.

□□□

HTO

Now, there are 5 ways to fill ones place.

Since, repetition is not allowed , so tens place can be filled by remaining 4 digits.

So, tens place can be filled in 4 ways.

Similarly, to fill hundreds place, we have 3 digits remaining.

So,hundreds can be filled by 3 ways.

So, required number of ways in which three digit numbers can be formed from the given digits is 5×4×3=60

Answer 2

Answer:

the possible 3 digit number