Question

2-digit numbers less than 91 which are 1 less than a multiple of 10

Answer 1

{19, 29, ... , 79, 89}

Explanation:

Multiples of 10 are {10, 20, 30, 40, ... , 90}

Numbers which are each 1 less than these multiples of 10 would be:

{9, 19, 29, ... , 79, 89}.

Note that the last number, 89, is less than 91.

We must omit 9 from this set, since 9 is not a 2-digit number. Then our final list is {19, 29, ... , 79, 89}.

Answer 2

The numbers are 19,29,39,49,59,69,79,89

Explanation:

2 digit numbers starts from 10 and ends on 99.

2 digit numbers less than 91 starts from 10 and ends at 90.

2 digit numbers less than 91 and multiple of 10 are 10,20,30,40,50,60,70,80,90.

2 digit numbers less than 91 and which are 1 less than a multiple of 10 are 19,29,39,49,59,69,79,89.

The numbers are 19,29,39,49,59,69,79,89