How many 4 digit numbers can be formed if repetitions are not allowed and the numbers always end with 3? - 405
- 450
- 540
- 504

448

Step-by-step explanation:

we have four spaces

_ _ _ _ but we know that they end in 3

_ _ _ 3 so the question changes how many 3 digit numbers can be formed without repetion and 3

so the first one has 8 options 1,2,4,5,6,7,8,9 we can have 0 here.

the second one 8 we count 0

the third 7 so we have

8*8*7*1=448

dont know why it doesn't fit.

for ex: the reciprocal of 3/4 is 4/3. it is the opposite.

reciprocal definition:

a mathematical expression or function so related to another that their product is one; the quantity obtained by dividing the number one by a given quantity.

x= cost per bracelet

number of bracelets * x + shipping charge = total cost

so

9x+9=72