Find the number of 3-digit numbers formed using the digits 1 to 9, without repetition, such the numbers either have all digits less than 5 or all digits greater than 4.

84

Step-by-step explanation:

Given,

The possible digits are 9 ( i.e. 1, 2, 3, 4, 5, 6, 7, 8, 9 )

Digits less than 5 = 4 ( i.e. 1, 2, 3, 4 )

Digits greater than 4 = 5 ( i.e.  5, 6, 7, 8, 9 )

Here, we need to make 3 digit number from these digits without repeating,

If digits are less than 5,

Then the possible ways = 4 × 3 × 2

= 24

If digits are greater than 4,

Then the possible ways = 5  × 4 × 3

= 60

Hence, the total ways of choosing three digits number without repeating if all digits are less than 5 or all digits are greater than 4

= 24 + 60

= 84

4 puzzles in 3 hours

step-by-step explanation:

it will cost dollar $540

the living room is 3 which means if we divide 325/3 then we get $108

therefore if 1part of the living room cost $108 and 3 costed $325

then total 5part of the room will cost 5*108 which gives $540