Question

How many 3 digit numbers can be formed such that, if one of the digits is 4, it has to be followed by
the digit 7. No digilis to be repeated in the number.

Answer 1

Answer:

15 numbers can be formed

Step-by-step explanation:

Condition is one digit should be 4 and followed by 7

and number should not be repeated and the number should be 3 digit.

147 , 247 , 347 , 547 , 647 , 847 , 947 , 470 , 471 , 472 , 473 , 475 , 476 , 478 , 479

Answer 2

If 3 digit even number start with 4 then next digit is 7.

So, numbers are 470,472,474,476,478=5 possibilities

Other 3 digits numbers can be formed as

(1) Unit digit can be taken from 0,2,5,6,8 i.e 5 ways

(2) Tenth digit can be taken from 0 to 9 except 4 (because if tenth digit is 4 then unit digit is 7 it is not possible) thus, 9 ways

(3) Hundredth digit can be taken from 1 to 9 except 4 thus, 8 ways

Hence 8×9×5+4=364 such numbers can be made.

Ans :-  3 digit numbers can be formed such that, if one of the digits is 4, it has to be followed by the digit 7 in this case, 364 such numbers can be made.

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