Find a trick here that can help you multiply a repdigit number less than 100 by a single digit number in less than 2 seconds as long as you know your multiplication table.
What is a repdigit number? A repdigit number is a number whose digits are the same. For example, 55 and 77 repdigit numbers.
What is a single-digit number? A single-digit number is a number that has only 1 digit. For example, 4 and 8 are single-digit numbers.
The trick to follow is shown in the 3 examples below
Example #1
44×9 = ?
Step 1: Multiply 4 by 9 to get 36. Write 36 down with a space between 3 and 6
Step 2: Add 3 and 6 to get 9
Step 3: Put 9 between 3 and 6.
44×9 = 396
Example #2
88×5 = ?
Step 1: Multiply 8 by 5 to get 40. Write 40 down with a space between 4 and 0
Step 2: Add 4 and 0 to get 4
Step 3: Put 4 between 4 and 0.
88×5 = 440
Example #3
99×9 = ?
Step 1: Multiply 9 by 9 to get 81. Write 81 down with a space between 8 and 1
Step 2: Add 8 and 1 to get 9
Step 3: Put 9 between 8 and 1.
99×9 = 891